Hi;Little out of the area here I suppose but working on a Motorhome with a 460 ford.Can't maintain enough vacuum to operate the controls for the heater etc.On hard pull the vacuum drops off and they go to a default position until can let up on throttle then vacuum comes back up and all is OK.Have had this same situation in cars with vacuum operated heater contols but just ignored it there.Is there some kind of pump that could be instaled to provide a little additional vacuum?As I remember my Olds diesel had some kind of pump to supply vacuum but I have no idea what was involved and that was long ago.Will get it to shop that has better equipment than I have to verify there is no leak involved too.Any thoughts would be appreciatted.