Bighare56

the engine runs anywhere from 1500 to 2000 rpm idling depending on the ambient air temp. When I first got it, it used to run right about 1000. I originally had a problem with the defroster not working properly. It wouldn't always close the valve to divert the air from the rest of the system to the window. I replaced the heater core and reconnected everything. It worked long enough to pass inspection, then the same problem started. I hand over handed the vacuum system and found the boots into the vacuum cylinder in the engine compartment had dry rotted. I replaced those with aftermarket off the shelf connections and again it worked for a little while. I suspect it to be a vacuum problem causing both problems, but am at my wits end trying to figure this out. Any ideas?