2000 Chevy Silverado missing during rain and moisture

I know the first thing on your mind is rotor cap and wires but it's been done plugs, fuel injectors, fuel filter, cat. Convertor, tps, have run seafoam thru the engine but when it rain there is a miss the miss is also there when the tow/haul selection is set to off, think that the dealer has replaced some of the value springs also the check engine light come on rarely then goes off after it dries up. The only code I get is "random cylinder missfire" could the ignition coil be cracked or not grounded well causing the miss


at wits end
shane