I have been chasing a misfire and rough idle since i got this car. Its an '02 vulcan. I have replaced the heads with remans with hardened seats, and replaced the dpfe, egr, egr solenoid, coil pack, IAC, cam sync, wires and plugs twice, all o2 sensors, pcv valve, maf sensor, all vacuum lines under the hood, and probably a few more things. All parts are bwd or motorcraft except o2 sensors and pcv valve. But i still have a slightly rough idle and an intermittent misfire on random cylinders. This week its cylinder 5. The idle has improved greatly from when i got it, and it drove fine on 2 300 mile trips, but its obviously still not right. I also have slightly rough 1-2 shift and 2-1 downshift sometimes, not sure if thats related. Any ideas?