Join Date: Feb 2005
Location: Athens, Greece
Re: 156 catalytic removal questions
I would suggest that you only remove the preheater cats on the exhaust manifold 2->1 part as i've done. Replace them with plain pipes with similar curvature and place the oxygen sensors at the same position they were before. Expect more low/mid range torque and better throttle response, but nothing conceivable at the high end. No reprogramming of the ECU is necessary after this.
I wuld not remove the main cat, you will probably get errors from the ECU because of the funny oxygen sensor readings and the ECU will run in "safe mode". You will probably have to find a way to fool the ECU into thinking that there is a "phantom" cat by messing with the oxygen sensor signal to get rid of these errors. Haven't done this nor have i heard of a person who has. Even a friend of mine with a heavily modified 1.8TS 240HP has replaced the stock cat with a racing one. I would suggest that you do this instead of totally removing the main cat.
"Black holes are where God divided by zero." - Steven Wright