Got the p0420..

[mnc2fan]

So cats probably bad. Wondering about what caused it. When I replaced my knock sensors a few months ago, I was putting the intake manifold back on, and tired torquing it down, and was trying foot lbs, not inch lbs on one of the bolts, but noticed it didn't seem right. I hear over tightening the gasket can cause a vacuum leak, so is it possible that is what caused that my p0420 code? Or have my 300k miles and 10 years old has done?

[GasGuzzler]

Miles alone have done it. Cat's dead, no questions.

[mnc2fan]

Thanks. Just being miles make my job easier. I'm thinking of just getting a nelson tune, and have the o2 sensors removed. Seems to be the cheapest thing to do, and cover the problem.