I've grounded everything in and around the unit, shielded the unit and the audio cables all the way to the amp, and grounded the engine block and the alternator, and replaced the ground to the battery. Not a hint of a difference no matter what I did. No other unit that I try in this truck has any problem.

 

Sorry to hear, could be a bad unit.
The unit I have is Chinese Joying knockoff that I got from eBay for $80.00. Its connected to a Boss amp with a 10inch sub.

I recall picking up a small blue device from Crutchfield back in the day when I had nasty ground nose from the radio.

 

I've seen that you have TorquePro, so you can have ODB parameters in your Disco?, which ODB unit / device do you use?

 

I use the OBDLink LX Bluetooth module.
I use it because it works with Robertf's GEMS Reader.app that resets Adaptives values.
OBDLink LX also comes with its own software app called OBDLink, this software only works with its hardware.