Truck appears to be running very well, but I now hear a new sound in the cab. It's a low hiss (sounds like air, maybe) and it gets louder when I compress the gas pedal. Is that normal? It's definitely in the cab and not a wheel sound - makes the sound at idle in parked position.
I know there are components to the system in the cab. It's a little annoying, so I'd love to be able to put a stop to it.
![Aggravated :banghead:](./images/smilies/banghead.gif)