Just bought a 2.0 TT used , 2200 miles that prev. owner had installed complete Oettinger exaust system fro turbo to rear (all stainless looks and sounds great). The problem is it keeps coding a catalytic efficiency fault. I'm told the only choice is to go to an APR chip mod. to change the linits in the program. Audi reset computer ($115 wasted) and lights back on. Anybody know any other fix besides going back to factory exhaust or spending $800 on the upgraded program. This car spins the wheels already without adding 50 more HP. Thanks Remodelman!!!