I have a 2005 F150, 5.4 triton. I bought the truck used and it came with an Edge tuner. It's lifted with 35's.

Under mild acceleration I get a psst-psst-psst-psst-psst-psst type noise. Sounds almost like air... It only happens in drive when you get on the gas and put a load on the engine but not always. It doesn't seem to happen if you mash the pedal...

I can't seem to replicate this sound in the driveway.


I've never heard this sound before. Any ideas?