My 4106 doesn't have a hand throttle, but it does have a fast idle.
The fast idle became common after the '04, because there no longer was a pony engine to run the HVAC, and you needed the additional idle speed to keep the HVAC system functioning properly while the coach was parked in revenue service.
OTOH, the basic coach chassis structure is very, very similar between the '04 & '06. . .Todd -
If you could post a photo of the governor housing on your engine, and the other things you have questions about, we could answer your question more intelligently. . .
FWIW & HTH. . .