I'm tryin to figure out what the heck is wrong with this truck. when i first got this truck it ran good, then i went an started it one day, and it started missing like an SOB. i tuned it up (plugs, wires, cap, rotor, fuel filter), and it still wont run good. i also noticed it sometimes idles up and down, instead of a good smooth idle, but not always. what can i look into? what should i try? getting this truck running will decide if i fix it or shit-can it! help me out!