CT-S4-Imola

runs great no check engine light, but when I go 100% on the throttle it hiccups. Perfect otherwise. Where should I start looking? Where is the fuel filter?

AvantS4me

https://forums.audiworld.com/s4/msgs/722730.phtml

quickaudi:STFA

have you scanned your car for codes yet?

DeutschlandATL

I think it's messing up, and perhaps sending wrong o2 info, resulting in an incorrect fuel/air mixture. Just my theory.

visintainer [vis]

pressure test for boost leaks

Seight311

Air/Fuel ratio... Maybe? Could be something simple thats only making a difference when the engine is running hard, like a really dirty air filter, dirty injectors, fuel filter etc. Maybe try and run like half a can of seafoam through the intake area, and dump the rest in the tank, I do that about every oil change and it seems to help a tad.

Someone with a similiar problem told me that they had parts of their cat falling apart internally, and under full throttle was when it really showed because the exhuast couldn't exit fast enough...

Im not an excellent trouble-shooter, just thought I would throw out my .02

informed

we had an A6 with a 2.7 in the shop a while ago with a similar complaint - ended up being a wery difficult diag. The wiring harness was getting chafed on a metal stud just below and to the left of the coolant resevoir.

DeutschlandATL

Yeah. 02 sensor, and postive charge deviation(hope I remembered that right)

quickaudi:STFA

pos. charge deviation means boost leak

Kartman

Fuel pressure, first the regulator then the pump