Nissan Repair: 87 300 zx stalls and wont run over 2k rpm, mass air flow, turbo air

Question
I have a 1987 300zx 5sp. Several months ago I noticed that it was using twice as much gas as normal and started running ruff and sometimes black smoke would come out the pipe. Now it is ok on gas but it stalls, has no power, hesitates in 1st and 2nd (like it can't gt enough gas, and will not go over 2000 rpm in any gear. I have replaced all the plugs, plug wires, distributer, and fuel filters. Is this the Mass Air Flow box that comes off the turbo air filter or is it something else or a combination? What should I start by replacing to see?

Answer
Hi Matt -

When you replaced the plugs, what color were the electrodes? And, were they the same color for all plugs? Or, better yet, can you check the color of the electrodes now?

I am thinking this is fuel related. The engine light on?

let me know -
aloha
calvin