Again I was having the same problem that you are having although I have the QuietPac 6500G model the symptoms are the same. On page 57 of your manual it shows a choke solenoid plastic boot. That is the same part that was causing my problem as it was contacting the choke and not letting it move smoothly. I put a spacer (Washer) in between the plastic and the metal and it solved my problem. I hope that this might help you.
Jack
2003 Rexhall Vision 27'
2019 Chevrolet Equinox
States we have been to with this MH