I have this weird Ac problem going on in my z. It works totally fine. It blows cold and the heat works great and it comes out all the proper vents. But what it does is if the turbo goes into positive boost it cuts out and doesn't work. it stops coming out the vents and doesn't even come out the defroster. Once it goes back to negative pressure everything works fine. All my vacuum hoses are good. I'm wondering if its my vacuum tank or vacuum pump that's the problem. Let me know what you think.

87' 300zx Turbo
Manuel Trans

 

Yes and/or yes. Check the tank and pump. Someone probably just hooked the vac line to the intake manifold.