I tried a little experiment. I have been reading about the benefits of removing the CAT. So I got myself a cheap Cat, gutted it, and stuck it on. I took her out for a spin and sure enough CEL pops on, not unexpected at all, but the code was not what I expected. Instead of the P0420 I have P2096. From reading this is generally caused by a dirty MAF. I have no objections to cleaning it, but it's just odd that it just started with the CAT removal. The car drives good, and it even yielded 20.2 MPG at 80 + mph on a 115 mile trip. Any thoughts on why this code would pop up other than MAF?

The car runs great, no negatives in that regard. It smells like crap though. I May have to put it back on, just for that reason alone. This pipe has no resonator, and I notice no difference In the sound, until you rev it up, then you can tell the difference. Just FYI for anyone that just thinks they have to have a resonator. I guess I will clean the sensor this weekend, not in the mood right now. Since it is not a DD, not a biggie.

 

I also have this same code via my mid pipe.. I fixed it with a new exhaust gasket.

 

Thank you. I will give that a shot along with a good cleaning.