I have a dog, not a cat - think that could be the problem?
Sounds like that might be where to look though. It's got 105k on it, both O2 sensors were replaced less than a year ago. If it was throwing a code, the check engine light would be on, right?
How do you diagnose a bad catalytic converter? (I didn't say cat jokesters)
Do I have to drop the gas tank to change the fuel filter? Sounds like a PITA.