My experience yesterday is the opposite.
Went in with a GDE tune the past 85,000 miles. Truck has 110,000 miles total. Did a fuel mileage check on the way in. Also got a feel for any hesitation with GDE.
After the flash I came home. Tested hesitation with maybe three hard accelerations, one from stop and two on the interstate. One was a merge situation and the other a pass at speeds up to 90 mph. NO HESITATION. No real felt change in poser either.
Fuel mileage going home was about 2 mpg less than GDE. Did drive faster going home and had at least one more acceleration/hesitation test. 28.1 mpg with GDE. 26.5 mpg with the AEM flash.
Expecting my new GDE program to arrive today so just waiting to get my engine back to clean running without the EGR and the DEF sensors. Now I also have a warranty to about 150,000 miles for near everything motor related. Unreal how much warranty there is. On top of that I am supposed to be getting $3,075. It would sure take a fool not to do that AEM.
Actually, I should be paying them for all the performance and pleasure the Ecodiesel has been to me the past 5+ years.