Error codes (p0420) - possibilities?

I have a 2006 Mustang GT and as of late it’s been throwing codes (P0420 and P0430 - catalyst efficiency below threshold both bank 1 and 2). I had it into the dealer (since it was initially hard to cold start and would produce smoke), the dealer said it was due to my AFE Stage 2 intake and oil filter which was over oiled and as such some of the oil had transferred onto the MAF sensor. They cleaned it and I had the same problem again, this time I purchased the AFE dry filter, sensor cleaner & throttle body cleaner and went to it on my own and cleaned everything out before reinstalling the dry filter, clearing the codes (oh btw I have an Xcal with Brenspeed tunes). Upon taking everything apart I noticed that the rubber seal between the throttle body and the intake had been significantly over tightened and over time had developed a crack. Could this be the culprit of the check engine light, rougher/higher idle etc.)? I’ve looked for a part number but haven’t had any luck searching for throttle body gasket (and TB seal), does anyone know what the part number is?<o></o>
Thanks,<o></o>
Matt<o></o>
 
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Do you have an Off Road H/X Pipe installed on your car? If you do, I think these codes can come up if you don't get the Rear O2's turned off in your computer program. If you don't, I think I remember hearing that air leaks on the Intake, MAF, couplings, etc, can create DTC's as well.