UPDATE: So I initially thought the zip tie completely solved the problem, but it didn't. I've been working on my truck this weekend and identified a potential fix. There is a bracket on the passenger side of the engine bay that attached the the muffler. I found the bolt that tightens the bracket was loose. I tightened it up and the vibrations in the cab while the AC is on and in drive seem to have gone away. Hopefully this is the long term fix.
