I found out after trying almost everything i could think of as to why my truck was running badly after i put the new headers, and exhaust on.... I had accidently switched the plug wires for the #2, and #3 cylinders! I feel like a dumbass!!! Sometimes, even the ones who know what there doing can mess up!

 

Can happen to anyone. Just be happy you found out before you dumped a bunch of money into it.