Truck fan fine when I bought it but needed headgaskets. Replaced headgaskets (plugs at the same time) and the truck developed a slight misfire but only at idle, ran good otherwise. Almost seemed to even go away once the engine was warmed up. Took the truck back to the shop that did the work and they suggested doing wires/cap/rotor, so all of that is new (including the distributor itself). Misfire was still there. Replaced MAP sensor with no help. Keep in mind i haven't gotten one check engine light. Drove it around for a while but that slight misfire at idle drove me nuts so i took it back to the shop again thinking it may have an intake gasket leak which they should cover having done that the same time as head gaskets. They said it wasn't the intake. Tried a new coil no help. Troubleshot it down to a bad injector so they replaced that, still had a misfire. Several others were cracked so i replaced all 8, still had a misfire. Took it to a different reputable shop and they checked timing and all sensors (everything functioned normally). Removed and cleaned the TB including new TB gasket with no help, did get a couple RPMS out of it though. Replaced the IAC (old one was really carboned up so i thought that was it) but that did not help either. Since i picked it up from the original shop after they replaced the coil and the one injector the misfire has gotten way worse, it has a bad surge at idle and the whole truck shakes, especially bad at a stop light with your foot on the break. It has also been hard to start since replacing the injectors. The truck has Gibson shorty headers and an aftermarket Y-Pipe so there are no pre cats or O2 Sensors at all (bought the truck like this). Truck has a K&N intake with a freshly cleaned filter. The only thing left that i can think of is the fuel pump or faulty head gasket. I NEED HELP. I have spent a ton of money trying to figure this out. NOTE: Truck seems to run great at anything above idle, runs and drives great until it drops to idle RPM.