2000 A6 2.7t 6SPD manual - No throttle response
 

I bought the vehicle 2 years ago and had my mechanic replace the motor and turbos. It drove fine until 3 weeks ago, when the throttle stopped working while I was driving. The EPC and Check Engine lights came on. Towed it home and have been having problems ever since. The car starts fine and idles continuously, but when I put it in gear, it stalls because there is no throttle response. Sometimes it works and I can get a few miles before it kicks out again.

When I run a diagnostics, I get 8 different engines codes every time. The codes appear to be random, with no frequent pattern. I brought it to the Audi dealership, they said they wouldn't be able to do anything until they put their own turbos in ($5000). I had an Audi specialist look at it several times, but he can't figure out the problem. We think there is a problem with the computer or electrical system but have run out of ideas. Any suggestions would be appreciated. Thanks in advance.

20k miles on the turbos, 80k miles on the motor, 180k on the body.

No response of the throttle plate to pedal input is NOT anything to do with turbo's. The EPC light (Electronic Power Control) indicates a throttle body fault OR a fault in another circuit that could cause incorrect trhottle opening has been detected and then the throttle body is disabled so you don't have a potential "Toyota" situation. If the fault is sporadic, the throttle will be enabled on the next key cycle.

The most common cause is either the terminals at the TB or faults in the wiring to the ECM from the TB. I'd check the connector at the TB first. Make sure there's no corrosion and the terminals are not spread. In rare cases it is the TB module itslef (part of the TB) but at $1,100+/- you want to be sure 1st. If all else fails, run what's called an "overlay" harness. Get the CORRECT terminals and neatly run new wires from the TB to the ECM. Generally you only need to do 4 of the 6 wires. Two of them are the power and ground for the TB motor. The other 4 are the VREF, ground and signal wires for TPS1 and TPS2 inside the TB assy.
Not saying it can't be but I've never seen a failed throttle pedal assy on an Audi. Just to be sure, take a look at the harness conector at the pedal position sensors connector on the pedal.

It would help if you could post the trouble codes you're getting. Preferably the Audi code and the OBD-II code (i.e. 18463/P1147)