Thanks a million for the help- I'm going to look into it. As far as the (possible 2) cats, the one you are talking of is the one on the bottom towards the exhaust (not the one coming off the engine) correct (if that's even considered a cat)? And, it is a Magnaflow cat (and muffler) on a catback exhaust system; should I try to match with the same one?

 

You only have one cat

 

Yeah, you should only have one cat. You have a magnaflow high flow cat on it allready? Or if you dont, It wouldnt hurt to put a magnaflow on it to make your whole system magnaflow. I put a OBX cat on a SRS system and it seems to be fine, I just made sure it was 2.5" inside diameter because my cat back and header are. I wold recomend getting it off ebay because they are so cheap, but I do notrecall seeing Magnaflow high flow cats. Hope that answers your question.

 

While we're on the subject, heresa stumper. I replace both primary and secondary O2 sensors, then put a high flow cat on, and I'm STILL getting the P0420. ???

 

the "high flow" cat is probably not doing anything useful, i.e. is it even a cat? or is it a test pipe?

 

Simlutators are a wonderful thing, so long as in your state they don't use a sniffer. Just get a sim. Makes things much easier.

 

hmmm. Yes Most high flow cats are not really cats. Usually when a code like that comes up it is because your computer is reading too lean or too rich from your O2 sensors. The secondary O2 determines that it is the cat that is not oporating right. I have not heard of this code coming up because there is a High flow cat instead of an OEM cat. Is that the only code you have? I want to say you are running to lean or too rich, but other codes should come up if that is the case. What kind of scanner do you have?
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