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Hello. Welcome to Just Answer. Please allow me to assist you. What you probably have is a faulty coolant temperature sensor. If it is reading incorrectly, it will reduce the pulse duration of the injectors. Additionally, these engines are notorious for vacuum line issues. If you have any leaking, cracked or poorly fitting lines you will get all kinds of problems. Look very close at the big tube between the air flow meter and the throttle body. Lastly, I would look very closely at the bolts that hold the intake manifold to the head. I have seen a lot of Z's that have had the heads of the bolts break off. This will cause a leak at the intake. This will give you too much air in the cylinders and mimic a fuel starvation issue. Please look at the items I have described; hopefully my suggestions will sort the issue out for you. If you have any questions, please feel free to reply. A positive rating for my input would be greatly appreciated. Thanks for choosing Just Answer.
One more thing I just remembered. Many years ago I had a Z with a fuel starvation problem. Try driving this car with the gas cap off. See if the problem ceases. If so, replace the cap. Try this before anything else.