grounding question

You need to move that ground wire, DO NOT ground to the seatbelt mount, THIS VERY BAD. In 95% of newer model GM vehicle, ground must be run directly to the battery, do this with the same guage wire as your power wire. I assume that you do not a have a dmm or how to use one so we won't talk about what you need to do with it to measure the ground resistance. If you do have one, great, let's get goin with it.Top Secret, I can tell you but then my wife will kill me.

Head into Radio Shack , they probably have a cheapy in stock or buy yourself a good Fluke DMM. It is a wise investment if you are going to pursue any interest ini car audio and security. An amp the size of that MTX needs to go directly to the battery for power and ground in this case. You must find away through that firewall or drill a hole a put grommets in place. If you do not feel comfortable drilling these holes or hole, have it done at any stereo install shop, they shouldn't charge too much for it. The holes in the firewall can always have rubber seal grommets inserted into them when it comes time for you to remove the stereo, as it is in a lot of cars from the factory. Expect to continue to have noise problems until you can get the power / ground issue resolved, unless it is a bad amp.Top Secret, I can tell you but then my wife will kill me.

it sounds like you probably have a bad RCA connection on your Amplifier

Does this truck have a boes system because if it does, I might the problem

Sorry, if this truck has a BOSE system, I might know the problem