I have a 1990 miata with 200,000 miles of pure enjoyment. I developed a pinhole leak in my lower radiator hose and in the process of replacing the hose I had to remove the Airbox and unplug the mass air flow sensor. When pulling the plug from the sensor wires from inside the sensor came out. So I've replaced the radiator hose, went on line and purchased a used mass air flow sensor, and installed it onto the air box and plugged in the wires. Car starts right up, idles fine, go to give it gas but it won't accelerate any higher than 2000rpms.
I purchased the mass air flow sensor spray and followed the instructions and I got the same results. I took my original sensor and put it in the used one , same results. I tried adjusting the position and spring tention of the sensor which then let me accelerate up to 2500rpms.
Do I have to disconnect the battery to reset then ecu or something on that line?

 

Sounds like a defective sensor. I'd take it back for another and see what happens.