1988 CV auto climate control problem

I replaced a leaky heater core in my 1988 Crown Victoria LX. Now, I have a problem with the climate control system in that I get heat when going up steep hills or on moderately hard to hard acceleration. All other functions work as they did before with panel, mix, hi-low and defrost air all routed properly. I get cold air the rest of the time as desired and the auto fan control and climate control system setpoint thermostat seem to be OK. The cold air comes back right away after I crest a steep hill or back off of hard acceleration.

I'm not sure about the vent function neither now or before. I saw a big flap picked yesterday when it was hot outside but I saw no movement of that particular door tonight (quite a bit cooler outside tonight). Also, if I turn the temp slider up I get heat (on heater functions, as it should) but I have not actually verified how that works while underway.

It was difficult to figure out how to remove the plenum and the Chilton's soft cover manual I have seemed to be of little help but I believe I got all connectors and vacuum lines connected properly. There are four vacuum actuated controls that I saw with three of them behind the ashtray and another behind the glove box. I should have made a drawing while I had the plenum out but I believe the control behind the glove box moves the isolation door directly in front of the heater core. That control seems to be more complex and there is an adjustable mechanism on it that I did move during the job (but tried to get back to same spot on reassembly). I'm thinking either this, a crossed vacuum line or an insufficient vacuum supply problem. I appreciate all observations and experiences. This is a stock, cherry car by the way that runs well.