help, P0303 misfire cyl.3 I checked plug,wire. and coil everything seems ok. volts from coil match the other one. P0422 cat. under threshold bank 1. what do I look for on this one ? I switched # 3 and # 2 plugs and the coils. engine was ok til it reached runing temp. then it started to run rough again. I cleared the codes and waitting to see what pops up since it is still running bad. some info. on what to look for or do would be nice.( when I said I switched the coils I just switched front to rear and rear to front.)