Customer Testimonials & Reviews

GDM Customer Testimonials

It’s one thing to promise excellence. It’s another thing to deliver it!

We let our clients speak for themselves. You talk. We listen. We would love to hear your testimonials about your experience working with us.


I have used GDM for my TDI tuning for the last several years. First up they did a stage 2 Economax tune on my 2012 6M MK6 Golf TDI. They did full race pipe EGR delete with full 3″ exhaust and GTI rear muffler (great exhaust option for super sound but still very liveable inside, must do for any modded MK6 Golf TDI!). Great performance and mpg upgrade, I’ve seen as high as 48 mpg, and even spirited driving resulted in 42 mpg or more.
Then my buddy and I added the CR170 turbo and GDM retuned with 4 bar MAP sensor Economax stage 2 and stage 4 tunes. They also installed a stage 2 South Bend clutch (and later upgraded to a DKM clutch). Still the same mpg on either tune, very little smoke and plenty of power. The support was great as well, any questions were professionally answered and issues resolved.
My most recent project has had them tune and delete my 2014 A7 3.0 TDI. Still great service from Ryan and any questions answered professionally. Once again I did stage 2 and 3 Economax tunes with the EGR delete. Exhaust is downpipe and mid-pipe, with stock rear muffler. Sound is very close to stock inside with a small increase in sound quality outside. Have yet to put on enough miles to report the mpg increase… but power is great! Tons of low end torque!
Thanks to GDM my TDIs run way better than stock on mpgs and power. I recommend checking them out for any TDI support!!

August 24, 2020

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I bought my TDI ECU and DSG tune through GDM. Les walked me through the steps for the remote tune of the DSG. I was impressed with how easy it was having never done a remote tune before. The ECU had to be sent to GDM for the tune but the turn around time was extremely fast. I was very happy with the process. Recently, a friend’s TDI needed a turbo replacement. GDM was the first place I thought of. I called Les and he had the turbo I needed at a great price. The turbo was delivered the very next day and I had the car running later that same day. GDM is a great company with efficient service! Will continue to be a customer. Thanks!

August 26, 2016

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Had my MK7 golf tuned and downpipe installed. Top notch work and great customer service. Had an issue with the tune file but being the great shop they are, they got me in straight away and cleared up the issue. Car runs amazing now and i am very happy with the outcome. Thx GDM.

August 3, 2016

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Richard Hupper

I got the DPF and ERG delete for my 13 golf tdi. After some time I decided to get a single mass flywheel clutch and Les talked me into the 170 turbo as well. I was nervous at 1st but I love my car so much now. Plenty of power everywhere and I can still get 53 mpg if I take it easy. 70,000 miles and no problems.

April 5, 2016

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I just wanted to share my experience working with Les and his team on my 2000 Jetta TDI. I think they did a great job diagnosing and fixing my problem (basically sluggish acceleration and an inability to cross 3000 rpm) After running tests on the timing and the MAF, they checked the EGR and intake and they were clogged beyond belief. They were quick and thorough with the intake cleaning as well the EGR delete and oil change that I decided to get. My mpg went from 42 on the highway to 48 on the return trip back. Being a first time TDI owner, I’m slowly learning the care and upkeep these cars need and I’m just thankful that I found a place that knows their stuff,charges very reasonable rates and are professional, friendly, and courteous. I hear of people travelling long ways to get work done on their TDIs and the best part is that GDM isn’t too far from me. I look forward to working with Les and Ryan and Ryan with my Jetta’s needs in the future.

March 16, 2016

Wes Frazee

Bought my 2012 Jetta brand new and Les and his awesome crew have worked wonders on it since I’ve had it. Car has had two different tunes, and currently running a stage 3.5 tune with the cr170 turbo. Everything they’ve done with my car has been done quickly and professionally and I recommend anybody with a TDI to them,not only for their quality of work but for their genuine kindness. Awesome group of people and look forward to dealing with them in the future.

March 8, 2016

Patrick E.

Being from the Baltimore area there are plenty of VW shops around town for both maintenance and performance work however none did work specifically on diesel or TDI Volkswagens. My recently purchased MK3 1.9 TDI was in need of both performance boost and my leaky pump sealed up again so my search for a knowledgeable TDI shop both started and ended at German Diesel Motorwerks!

I scheduled my appointment and took the journey to Les and the Ryans (yes there are not one but TWO!) up in PA where I was greeted with a very knowledgeable staff of professionals that did more than took care of my MK3. They sealed my pump, pop tested my injectors, replaced the nozzles, and threw a Stage 2 tune on my vehicle in good time and at a very fair price! It doesn’t get better than GDM if you need any TDI or diesel work done. On my way home the torque increase from the work they had done had me smiling the entire way! Two thumbs up for these guys!

February 26, 2016

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Matt R.

Les is hands down the best Tdi guy on the east coast. I sent him my 2006 golf Tdi for some performance up grades. Vnt 17 turbo, new stage 2 cam, alh intake, full exhaust, stage 4 tune, and a bunch of other odds and ends. This man knows his tdi’s! My car is night and day difference. Les and I spent a few hours talking about every detail from shipping my car from Cleveland Ohio to his shop and the work that’s going to be performed. He went above and beyond what I ever thought. He answered all of my questions and concerns and also gave me his personal cell phone Incase the shipping company showed earlier than expected.

Trust me! GDM is an awesome shop and they definitely know their stuff about diesels

February 25, 2016

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Glenn W.

I installed the GDM down pipe and deleted the cat/flapper/resonator as well. Les at worked with me to get what I needed for the car and helped with cost, I am a disabled Veteran from the Vietnam era and driving my Jetta is one of my joys in life. The car is a 2012 Jetta TDI sedan with premium package and DSG trans. As a stock vehicle we averaged just over 43 MPG for the first 41 thousand miles (tracked on On the first trip after the install we got an amazing increase in mileage but thought it best to do some more testing before writing a report.
So here are the results from the last five fill-ups and trips. All trips are in 70 to 80 degree weather on roads in Arizona, trip three and trip five are the same exact route (except for our lunch stop place) and used the same station and pump. The car is always filled to “wet in the neck” a condition that has liquid diesel standing in the filler neck, not foam but actual liquid. All trips had the air conditioning on and were driven by me with the wife riding in the passenger seat. Tires are set at 45 PSI and a K&N air filter install when the car was new.

As a side benefit the tune cured all the low speed regen bucking and stumbling that the dealer said they could not replicate in their test drives. Also there is no turbo lag during idle to pulling out in traffic.

Trip 1. Casa Grande to Gila Bend to Ajo to Organ Pipe Cactus National Park back to Casa Grande via Indian 15. Total miles 270.3, gallons used 4.724 MPG 57.218. The trip is approximately 90% two lane roads with speeds of 55 to 60 MPH and 10% town roads with 35 to 45 MPH limits.

Trip 2. In town (Casa Grande) short stop and goes for several days. Total miles 140.3 gallons used 3.044, MPG 46.090. The trip was 95% town and 5% highway.

Trip 3. Casa Grande to Los Algodones Mexico back to Casa Grande via highway I 8. Total Miles were 379.9, gallons used 6.973 MPG 54.482. The trip was 95% highway and 5% in town roads. Speed on the highway was 65MPH using the throttle manually (no cruise control).

Trip 4. In town (Casa Grande) short stop and goes for several days. Total miles 119.2 gallons used 2.529, MPG 47.133. The trip was 95% town and 5% highway.

Trip 5. Casa Grande to Los Algodones Mexico back to Casa Grande via highway I 8. Total Miles were 374.5, gallons used 7.158 MPG 52.319. The trip was 95% highway and 5% in town roads. Speed on the highway was 65MPH using the cruise control, and very little manual throttle use.

As you can see the car responds well to the tune and pipe, better on the lower speeds as opposed to the constant highway speeds, and better with manual throttle than with cruise control. I think the better mileage in manual throttle control is due to being able to see hills and respond easier to accelerations and decelerations then the cruise controls more rapid responses. I can build up speeds for hills at an easy pace rather than the cruise controls instant response.

In summary, I am extremely pleased with the modifications to the car and will realize a payback in savings much sooner than I anticipated. So if you are on the fence about spending the money do not hesitate it is well worth the time and money to make the mods.

January 28, 2016

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Just wanted to say how pleased I am with Les at German Diesel Motorwerks. I recently got a stage 2 ECU tune, DSG tune, GDM downpipe and racepipe. I also got a resonator in the midpipe which terminates into the “cat-back” portion of the stock exhaust.
I am very happy with Les’ service and the performance my car now has. I am also glad that I no longer have any EGR clogging up my intake and gumming up my turbo vanes. I had the stage 1 APR tune before and was happy with it, but I wanted more. I also wanted to delete the DPF/EGR system before it became an issue.

I have noticed slight MPG gains so far, but I haven’t been keeping my foot out of it either. Most people have seen an increase in the 4-6 MPG range, so that’s what I expect as well.

The only thing I’m a little disappointed about is the exhaust note. I read in several different forums that the car would sound stock with either a resonator OR the stock muffler in the exhaust flow path. Well, I have both and the car is louder than stock. I am going to have to add another resonator and/or muffler if I want the sound levels to be stock. Other than that I have no complaints.

I would highly recommend these mods to anyone thinking about doing it. Do it now, do not wait! You will be happy you did! And if you are on the east coast I would personally recommend Les at GDM.

January 24, 2016