shut down the truck, wait a few sec and it whistles at me a couple of times as i walk away (mostly when its hot).

i know i take pretty good care of her and such, but i hope this separation anxiety is'nt going to turn into an unhealthy obsession.

sounds like its coming from under the truck. cat maybe?

99 f150 4.6 120k

 

have you added any aftermarket parts lately like a FIPK K&N filter? My truck has always made a hissing sould through the FIPK filter since day 1, cause my dealership installed it for me. I have a 2003 fx4 supercrew and it has always done this when i shut her down.