Hiddendragonse,
Sorry to hear that the CEL returned. If you haven't already, do a search on 420/430 and you will see many, many threads about this. It is probably failing cats or bad O2 sensors. You will see in the threads, that there is a 80,000 mile warranty covering the cats. If there is any question and you have < 80K, get them replaced because they are very expensive.
