Fletch

There is speculation that the cat might be "choked" or something and throttling the exhaust note. ???
dunno.
The manifold was replaced and some crap may have got into the cat and screwed it???

Either way, it'll be one more thing eliminated.

mikey k

True True - I know the feeling trying to eliminate alternator whine from my ICE

Chris Type R

If only I could eliminate the whine from my GF

Ali_McBlue

for Chris

Paper Lawyer

that's a good suggestion Ali tell us how well it works Chris

Chris Type R

mikey k

Does that work for whining ICE as well

Chris Type R

I might need some ice after a

mikey k

Good One

Turtle

The cat is pretty tough - aside from forced induction, they don't seem to be breaking up. There are two sections inside it - one either side of the secondary O2 sensor. If the front section is damaged, it'll normally trip the CEL as the readings for the secondary O2 sensor won't be right. Taking the cat off without changing the ECU will give a CEL which will complicate any proper diagnostics. Sure you can fit an O2 simulator and hope to stop the CEL, but if you're decatting for performance the standard ECU isn't going to help you anyway.

Resetting the ECU now won't really tell him anything. He needed to do it before changing anything else.

-Brian.