so at first i thought it was the intake that i did(homemade type) but its getting worse and its not coming from the intake, ive gotten under the hood and crawled up in there and it seems to be coming from the back right somewhere, it was dark and i was crawlin around with a flashlight so i dont have to much to report over it, but its a 98 f150 with the 5.4 with 113,000. oh and it threw a CEL. so im goin into the shop tomorrow morning toget it checked out but if any of you can give me a hint as to what it is before i do that and maybe if i can fix it myself that would be great. im fairly good with a wrench so idk we will see i guess. thanks,
Scott

 

Until you see the codes, my guess is they will be lean codes from a vacuum leak that is causng the whisle.
It should be easy to find with the engine runnig..

 

yup, took it in the shop this morning, right on the money, vacuum leak. its going to get fixed monday when they can get the parts in.