Your car is running rich.If you smell rotten egg's that means your cats are working properly.For the cats to clean up unburnt fuel it goes through a chemical and heat process,one of its effects is the rotton egg smell.If you smell it,your junk is workin,and workin hard.Your car is running overly rich and the cats are workin overtime to clean it up.I highly doubt that magnaflows cats are gonna clog.Any one who says that the rotton egg smell means they are bad,has to take another look at it.
I agree with facemelter. Rotton eggs means the cat is WORKING, and that you are probably running a little too rich. I just put in new cats and they smell like eggs after I get on the gas, and I know it is running a little too rich, I'm still trying to tune the thing (I have a carb). Plugged cats mean loss of power and higher emissions, since you are running really clean, I highly doubt there is anything wrong with the cats, just a tuning issue you need to find.