I have a 1992 Chevy Astro 4.3 Vortec. When the PVC valve is connected it stalls.

Just because .......... the PCV valve is a one-way check-valve, so when you say you can blow through it , you do just mean in one direction right? Have you tested the IAC? May be stuck at closed position. If your good at improvising , try plugging in the PCV and removing the IAC and manually restrict the airflow from there (that's where the improvising comes in) see what that does and go from there as necessary. May just be stuck from carbon build-up and sitting for a year , but also may be a control problem , so don't just throw a part at it without some sort of verification. Good luck.