I have a 3.2 which has 4 cats; a pre-cat and a main cat, and 4 O
2 sensors. this is 2 of each per bank.
There is a known issue on the 3.2 and 2.6 DBW engines that codes 0420 and 0430 come up to tell you that the pre-cats are "tired", this is a measurement of the difference of the exhaust mixture from the primary O
2 sensors in the series to the secondary.
Moving the secondary O2 sensors "tricks" the ECU, by cleaning the air through the main cats.
I have done this. When I had my stainless steel "cat-back" exhaust system fitted I had them add some O
2 sensor bosses behind the main cats and blanked out the original bosses with plugs. This has solved the initial problem of the 0420 and 0430 codes.
My question is this:
My car effectively no longer needs the pre-cats; would I gain much, if anything, in the way of power by replacing the front section with those from a 3.0 thereby removing the pre-cats?
My thoughts are that the pre-cats must be causing a degree of back pressure and I would have a freer flowing exhaust system without them. That is ultimately why people de-cat track cars and fit "sports cats" to their cars isn't it?