After the car was tuned it ran pretty well. A couple weeks ago I got a CEL. Read it to be P0172 (running rich), P0102 (MAF) and P0420 (cat). It would come and clear itself within a few drive cycles. Car ran fine, though.

Finally it stayed on for quite a while so I read it and cleared it. It went away for a few more drive cycles and now the CEL returned and is flashing, but only showing P0172 (running rich) and P0300 (misfire).

Seems like I got alot of stuff going on. First I plan on loading a conservative timing map. That tends to eliminate the misfire code. So far the only code that I've been consistently getting is the rich code.

Where should I start? Clean the MAF; connections look good? Check the 02 sensors? The front one is about 20K miles old. I'm definately getting reduced mpg this tank. Other than that, the car still runs great.