If its happening without keying the mic, sounds like the truck itself has issues. Nothing to do with the radio.
Best to have your power source straight to the battery, and not use factory connections. That goes for low, medium, or high power radios.
Run your own coax and antenna, don't use factory installed. Most factory installs provide signal for am/fm radio, tv's, cb's among other electronics on the truck.
Bond your antenna system to the truck and frame. There are several threads here onthe forum as well as numerous sites on the internet to explain.
These are just a couple things I've run into myself. Hope this helps ya out