I had this problem a few years back changed fuel pressure reg, fuel pump, injectors, distributor cap,ext ext. eventually the local mechanic said the rings were bad and I may need a new motor. so i took it to the dealer ship had them diagnose the truck and it came back as a bad ecm, the cars computer, paid 250$ for the dealer to tell me that .. then got the ecm on ebay for 45$ could have saved 1750$ had i went to the dealer first for the proper diagnoses
EDIT you will save alot of money if you go to the dealer for diagnoses then use ebay and a book to fix the problem.