Lt1 misfire

[Aaron G]

I have a 94 Buick Roadmaster Lt1 that has developed a misfire/dead cylinder. I drove my wagon to get pizza ran fine, came out had what felt like a dead cylinder. I made it home the driver side bank was making a huffing sound at the exhaust tip. I have so far checked the compression 150 psi each cylinder and checked spark at plugs with a spark checker I have spark at plugs. I have discovered recently that moisture causes car not to fire at all motor spins over but no spark. I have not replaced anything yet all parts appear stock car has 220,00 miles. Thanks in advance for any help you guys can give.