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Discussion Starter #1
Hey, guys. I'm new to the forum and quite honestly a novice with car tuning and only moderately adapt at car modification so apologies if I'm missing something extremely obvious here and for the wall of text.

I have a 2005 GTO (LS2) with 74,500 miles on it, aftermarket intake, headers, exhaust and cats (everything done prior to me purchasing the car).

  1. My car began to have a terrible misfire on the passenger side, problem was isolated as a leaking header gasket that was throwing off the sensors.
  2. Took the car to a tuner where we replaced the plugs and wires.
  3. Since we couldn't get a gasket right that minute the tuner opted to lock a tune into the car and disable the O2 feedback so the car would be drivable.
  4. Fixed the gaskets a week later then re-enabled the O2 feedback
  5. I usually only drive the car in 10 mile chunks but after a long city-wide drive the car threw 4 codes at me: P0172, P0172, P0420, P0430 (bank 1 & 2 too rich and cat bank 1 & 2 under performing)
  6. After the car sat and cooled down the CEL cleared itself.
  7. For a test I drove the car across town again (mostly highway) and the code(s) popped up again.
  8. Same scenario: let the car sit overnight, code clears itself the next day
I thought maybe the cats are going bad but they're only 1 year old (bought the car catless and had to have them placed on the car).

Does this sound like a bad cat issue? I don't want to throw parts and labor to replace the cats if it's not the route cause of the issue.

Thanks for any help.
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