Nissan Repair: idle issue and no boost pressure., fuel guage, engine vacuum

Question
I'm working on a z32 90-96 300zx twin turbo. Not sure where to start. This car won't idle on it's own and does not build boost under a load. I have to push the pedal to the floor to build about 4 pounds of boost and the car will not idle on it's own when cold. if you keep it revved up it will stay running and when it gets warm it will idle. Car never runs like supposed to. It sputters and is black smoking. Running rich. Even the air fuel guage says it's dumping in fuel and not getting enough air. Any help appreciated. thanks

Answer
Hi Chris -

I think the brake booster assembly is defective. there is a diaphram in the middle of that thing, and is run by engine vacuum. Perhaps that diaphragm is ruptured.

Remove and plug the hose that goes to the brake booster. Start the engine and see if the problem with the idle persists. If not, then replace the booster assembly.

Hope this helps -
aloha
calvin