whats up all... just finished my 2002 A4 1.8t project build and im at a brick wall! the car runs great for the exception of the higher revs off boost on the highway. Im not getting any codes and i can rule out the coil packs for they are all new ! plus ive already swapped each one out to see if there was a possibility of a defective one, as well as all the vac lines and Hoses. when on boost (T3/T4 9psi stock pressure) she runs like a champ, clean straight through the revs with lots of pulling power and no hesitation but normal driving around 4k RPM i get some slight bucking. I was thinking possibly bad gas or maybe even secondary O2 sensor to close into the exhaust stream (no cats), but i am at a loss. Cant put my finger on it. I really would like to iron out this so i can move foward with the second part of my project. Your thoughts....

As of now I am running on stock parameters. The only upgrade that needed to be installed to get it running was the turbo. I have a 630 file with 630 injectors and all the goodies that go with it i.e. fuel, wideband, FMIC, pluming, MAF,brakes,axles... ect, but haven't installed as of yet,thats all in my nxt phaze.The entire intake system was installed with the big turbo as stock to avoid any silly check eng lights. Unfortunately I have no codes but get a flat spot around 4k off boast.

Thanks for all the advise! i think it was bad gas... it just stopped out of nowhere. The car is running great.

Thanks again....