2001 S4 feels like it's in limp mode, not boosting at all. Pulling codes reveals P1639 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal

I just changed the cv axles and haven't driven it much since then, pulled out of parent's driveway otw to my house 4 hours away... and now this.

Does anyone have experience with this?

 

no experience myself but it would seem the pedal assembly is messed up. I don't know how they work but perhaps you could clean up the contacts. I'd imagine it reads pedal position like a fuel float reads fuel level