1990 Mazda MPV Engine dies

Engine Mechanical problem
1990 Mazda MPV 6 cyl Two Wheel Drive Automatic 250K miles

Hello and Aloha -

I just replaced the head gaskets and timing belt on this vehicle. Car runs great and smoothly in park, but as soon as I put it in gear or turn the A/C on, the engine dies. I am thinking the vacuum lines are not routed properly? I tried to replace them where I found them, but perhaps you can guide me in the right direction on where to look? Is it even a vacuum line issue? I am thinking there must be some sort of solenoid that kicks the idle up when the A/C is turned on. If the engine survives the shift into gear (sometimes when I shift it, it drops to about 400RPM and then levels off about 700), it will idle great in gear. No drivaeability problems once I am on the road.

Appreciate the help -

calvin