[darkpuppet]

looks like the car could be running a little rich... check the spark plugs, make sure they're not fouled, O2 sensors (why you'd need to check this again, not sure -- they should last more than a year), clogged air filter could do it too.

after that, you can try to find a gas station that puts alcohol additive into the gas to help lean it out a little....

of course, if none of that works, it could be that your cat is done for...