It feels like i have a potato in the exhaust. I changed between different ecu versions and the problem ist still here. At 2900 rpm i noticed a bucking (yo-yo). Could this problem due to an incorrect adjusted bypass valve? I have no error codes in the ecu.
I installed the VGS system and the bucking at 2900 was more noticeable than without.
Could it be due to an leak in the vacuum pipe or another pipe??
I hear a noise under the intercooler which I think it isn't normal.

I hope anybody of you US-guys could help an European-guy. Thanks Peter

 

It could be a bad Bypass Valve. I have read of several BPV go bad. The noise you have under the IC sounds like it needs to be checked. First thing that comes to mind is if your car is an 02 or 03, there was a problem with the PCV tube. Look at this tread:

https://www.northamericanmotoring.co...light=pcv+tube

I hope this helps.

Bomboasy