I recently installed a K&N air intake on my 05 f150/w 5.4 and noticed a hissing sound under the hood during acceleration. I think it's just the intake sucking air, but wanted to see if anybody has came across this or what your thoughts my be.

 

that hissing sound is perfectly normal. its just air getting sucked in. my friend just changed his aftermarket intake to a k & n intake and the hiss got louder but added more horespower

 

Yep, that's pretty much it. It's normal. Get a Magnaflow or Flowmaster exhaust and you won't hear it anymore!

 

thats not really true. even with a magnaflow or flowmaster exhaust kit the hissing may still stay the same

 

Yeah, AF1 with a Borla cat-back and I can still hear the induction sound, I love it..

 

Mine does it too, you get used to it, sounds kinda cool after awhile

 

It's just me, but that noise would drive me nuts...

At least your OK with it.