6.0 L Misfire

[maxdaddy00005]

I recently had a set of long tube headers installed on my truck. When I went to pick it up from the shop I immediately noticed that it was missing real bad, especially under hard acceleration. When I looked under the hood I noticed that several of my orginal plug wires were contacting the header. I replaced these wires with new MSD wires, so there are no longer any touching any of the header tubes. This definitely helped the problem, but I still noticed it missing under acceleration. Sometimes it missed bad enough to throw a flashing SEL that would last for a few seconds then go away as soon as I let out on the throttle. I hooked up a scan tool and found that the truck was missing A LOT at idle on all cylinders, but 10x's as much on cylinders 1 and 8 as the others. The miss disappears while cruising. I've changed the coils around and the miss does not follow the movement, so I dont think I have bad coils. I did replace the fuel filter and the definitely helped straighten up the miss at idle. Now it misses occasionally while idleing and under hard acceleration. I just bought some sleeves to unsulate the plug wire boots and will be putting them on tonight, in case the wires are still too near the header tubes. My only other thoughts would be a possible vacuum leak? Any ideas.

Just a note- I've also had lots of trouble with the truck stalling, but this problem began way before I had the headers installed so I don't think that it is related. It usually only stalls when I am in reverse and turning the wheel at low RPM, like backing into a parking spot. Like I said I don't believe the problems are related, but if anyone has any suggustions for either problem I would be very appreciative.