[Steve Tinker]

I don't think the coil wires will reach to different cylinders.

tada - have you used a Durametric to check out possible problems? You are chasing your tail without some form of scanner to give you some clue as to what is going on.

If all 3 cylinders on one bank are failing to fire (I assume the offending header pipes 4,5 & 6 are still cold even after the engine has run on cylinders 1,2 & 3), then I think you have a deeper problem than an air/fuel/spark failure. I can understand losing one cylinder due to a fault, but not three - especially all on the same bank.
After a compression check (which is a must) plus a comprehensive Durametric analysis if possible, a more serious mechanical problem is in your future, like bent valves - which a compression test will show - or valve timing issues.
If you do complete a compression test, just make sure you remove all plugs first, remove the fuel pump fuse & make sure the throttle body is fully open (foot hard down on the accelerator pedal). Then start on the "good" side to get 3 x comparable results before going over to the problematic side.