Hello Ed. DocMike here, just checking in to see how Thor Forum is doing and noticed that your Manual is still a hot number. We sold our Thor Vegas 3 years ago but we are still active with RV'ing, which is why I am sending you this message.
The Ford V-10, used in many makes and models of RV, has a history of making a rattling sound at around 2100RPM (due to harmonic vibrations in the serpentine belt) for many owners. I recently fixed mine on our Nexus Viper 27v Class C.
I posted the fix yesterday there on Thor Forum under Maintenance and Repair, under a thread started by "Laid to the law" on 30Mar20. I am about #48 on the comment roster there. Since the problem is occurring in Thor products and the problem's fix is under $45 if you do it your self, I thought it might be worth noting in your Manual. I've included part numbers (2 parts needed, a bolt and the pulley) and a couple of pictures in my posted repair.
Hope it helps others.

Take Care.
DocMike

Mike -- did you post a schematic for the fuse panel in the compartment under the driver's seat? If so -- can you forward it to my email -- bevedfelker@live.com.
? Thanks. Ed