I have a 1990 300zx tt that im haveing a lot of problems with at idle aftet the car has wormed up the vacuum jumps between 10 and 14 and when i pump the brakes it sometimes dies or the idle goes down to like 300 to 500 and the vacuum also goes down to 5 to 8. This also happes when i cut the heat or a/c on. Ive tried to adjust the idle but when i pluges in the aac it doesnt change the idle

Find the vacuum line that goes to the Brake Booster , disconnect it where it comes out of the motor's manifold ,
then blockoff the " now opened " manifold fitting - see how they run ?

CAUTION : you'll NOW have No POWER in the brakes , test idle rpm's sitting still , seriously familiarize how much increased brake pedal force is NOW necessary to slow or stop the car , IF should you want to "attempt" to drive.

Has someone removed your aicv's and not lugged the other side of the solenoid? Might want to have a look at the aiv system.