so, i decided tochange my plug wires and plugs, the stock ones where melterd...

anyway put on msd plug wires for the 8.1L and then the stock sparkplugs... truck drive fine for 50 miles ( afternoon) then it started missing. cylinder 1 and 3.. so today i checked all the plugs.. all are on and like new, (put on thursday). its so out of wack it back fires ideling...

thought that maybe for some strange reason it had fauled the plugs... so i pulled all the plugs and they look brand new as well, i rechecked the gap and they are 55, gm calls for 60 but i a lot of people gap them down to 55

used the scanner everything was fine, no missfires, knock or anythng.

drove 20 miles and bam... out of the blue service engine soon blinking and the miss is back...

so, is there any way to test the coil packs?