1989 Toyota Other Idle-up magnet valve for AC

This is a long story, so bear with me.

Does anybody have a airflow diagram for an idle-up magnet valve, or alternatively, explain how the flow works with AC off and with AC on.
The diagram attached is a Toyota Magnet Valve and Diaphragm

If I follow the pipe connections as per diagram, the outer pipe with the one way valve attached, connects to the outside of the diaphragm with the other end connecting to the 1st pipe (outside) of the idle up magnet valve
It appears that the airflow comes from the diaphragm to the IU only when the AC is switched on

The second pipe connection as per diagram runs from the inside pipe of the IU and connects with the body on which the diaphragm is mounted. This particular connection on the body sucks air even when the AC is off.

As both of these units have just been replaced with OEM parts, I'm still experiencing engine stalls on cold starts. When the Ac is switched on, even after adjusting the idle speed.

Normal idle speed is 700Rpm without AC. Turning on the Ac at idle will bring the RPM up to 1200 for a few seconds, then settles at around 900RPM. But if I cut-off the AC at idle, the RPM will drop to around 400 and the engine will stall.

I have checked all the connecting pipes for cracks, and they are OK. Mostly they are new pipes.
I have checked to see that the one way valve in the IU pipe is properly connected, and it's also OK


The first thing I need to know is, have I got the pipe connections right. It would be useful if I knew how the airflow is supposed to work with and without the AC

Hope somebody out there has a solution. Just keep in mind with your answers I'm no techie mechanic, just a DIY learn as you go guy, so simple answers please.