after i turn off the engine there's a hiss for 20-30 seconds in the passenger side of the engine compartment toward the back. its not very loud, you can't hear it inside at all. i found this symptom in another post and it seemed like it might be normal but no one ever confirmed. ive only had the truck a month but its a quiet enough sound where it easily could have been there all along.

other than that my only problem is running over hummers and jeeps.

 

No worry. It's the high pressure side of the A/C system bleeding down.

MikeyB

 

As MikeyB said. Bet if you turn the A/C off for a few minutes before you shut the engine down that you will not be able to hear that sound any more.
It's normal.