i have a superchips programmer on my 03 5.4 i have been told that using plugs other than the autolite or motorcraft plugs will cause problems. my question is do i need to use the ford plugs or can i use a better aftermarket plug since i have a programmer. also, are cold air intakes worth the money?
You will not gain anything with aftermarket plugs unless you have a supercharger or are pushing 350hp with a N/A engine.
On FIPK's It depends on what you mean by worth the money, I like them because you no longer have to buy a $10-$20 air filter every 15K miles. I never noticed any performance gains with mine although it did seem that throttle response was a hair better. I would guess with headers, bigger exhaust and a tuner a FIPK might net you some performance but I don't see it happening by itself.