GMC Repair: misfire after warm up, gmc syclone, fool proof

Question
i have a 1991 GMC Syclone. Its a turbo 4.3 awd sonoma. The truck will idle and run fine until its warmed up. usualy after 10 min. Then it has a bad misfire. The warner it gets the worse the misfire is. To the point it pops 2-3 times a second. I have ran a Datamaster program on it and found no problems. All values are normal except the idle going up and down 200 rpm. I can see the enginge shaking. I have installed new cap, rotor, wires, plugs and coil. Plug #1 looked wet the first time I removed it but when I removed the new one it looks like all the others. Compresion test was done on a cold engine with all the plugs removed and all were in the 150-160 range. Please help. What else would cause a missfire on a warm engine? Thank you

Answer
Normally I would say an ignition coil, but in this case maybe not.

I would try a compression test on the engine while it is warm, also try removing the plug wires one at a time to find the missing cylinder. To do this I would let the engine warm up so that is was missing and then turn it off and take 1 wire off of the cap and see if it makes a difference. The cylinder that does not make a difference is where you should focus your attention.

Also does it get better or worse if you power brake the truck, generally low rpm misfires are from fuel, and high rpm misfires are from spark. This is not fool proof just a general thing, I have found opposites before just not many.