I have a '04 F-350 4x4 and I've got several problems with it. First is that if I have my ac or heater on when I switch my truck into 4wd it kicks my vents to the defroster ducts and blows really hard. The second is This truck is really hard to start and when it finally does start the truck shakes terribly bad and the exhaust sounds really choppy and blows white smoke .It takes about 30 minutes for it to get enough power to even move in reverse. Then I can run it all day ... Still shaking terribly bad... and randomly it will run great then go right back to shaking and smoking . I took it to a local dealership and they said it was injectors , and that they had a program to re calibrate my injectors to change how much fuel they sprayed. That didnt work ... so I took it to another shop and they ran the codes and it didnt flag that the injectors were bad but that they had low voltage . They erased all the codes and said they fixed it.. It ran great for about 6 hrs. and started doing it all over again .... I dunno ... just wondering if I just need to go ahead and change these injectors and get it over with. By the way my truck has 132,000 miles on it and I've got a banks 6-gun bundle with a 5" downpipe and 4" straight pipe .