hi all, had the car 3 1/2 years virtually trouble free, but did get an engine warning light not long after purchase which my reader indicated bad cat or o2 sensor. Clearing the code would get rid of it for 50kms or so, but it always came back..basically ignored it until a few months ago, when I got flashing red warning and " cat failure" or similar come up on the dash display and the car went into limp mode so I pulled over and stopped and turned it off. I waited a minute or so and restarted , and no fault came up, and no check light has come on since...and its run fine .Eventually took the car to have the cats replaced yesterday , as I've been told them clogging up is common, but the local shop basically hadn't seen cats with an 02 sensor in them, so was stuffed and couldn't do it... ( I'm pretty rural ) So the questions are, if no codes do I worry about it, and if I still should whats a good source for new cats online? TIA Dean