Hey guys I've been looking into it and have been trying to trouble shoot it for the past 2 weeks. Endless internet research. The problem got worse after i swap spark plugs with Acdelco Iridium spark plugs. The mis fire would be a random surge when at idel stop but once in a full moon after the swap of plugs the truck when cold has multiple mis fires and once warm goes away. I've replace spark plugs, battery, coolant temp sensor. I've been thinking about switching spark plugs to try my luck. Last thing I'm wanting is the head. It's a 3.5 i5 with 148,000 miles any light or info is greatly appreciated.