300zx barely idles and revs are limited
 

1985 300zx 2+2 manual n/a t-tops maroon with an analog dash.. 276,000 miles

Went to start the Z today, and it idled a little rough as it always does (ONLY when cold, i guess chts) and it warmed up normally. took it around the block, and noticed a DRASTIC increase in power. It has never been that fast.

Anyway, I went to hit the gas a second or third time, and I was jerked forward.. the car would not exceed 1500-2000 RPMs..if I hit the gas, it would stumble and nearly stall. .if i pushed the clutch in, it would go to 300-500rpm, and then stall. I limped it to a gas station, thinking it was low on fuel. Put 93 octane in as I always do, and started it up. same idle problem, only now my rev limiter was limited to 3500 RPM. AFTER fueling up, it still had the same idle problem, but now if I hit the gas, it would run normally except to 3500rpm. I got the car home safely.

Where to start.... Fuel pump, grounds, or ECU codes?

Yes.

I have to leave for work in a few minutes so I didn't get to read the codes yet. But I played with it more, no change still. i noticed that at other throttle positions, that "governed" rpm is lower. at about half throttle it seems to be governed to 2000. Occasionally it makes a LOUD backfire, suggesting the mixture is off or something. I heard a noise that sounded like drinking from a nearly empty cup from a straw, maybe the fuel pump is bad afterall.

Air Flow Meter
 

My best guess is the Air flow meter (silver box on the intake, next to the fan, drivers side) is intermittently losing connection. Unplug the connector and look for any corrosion on the terminals and clean accordingly.

The engine retards to 2000 rpms when the air flow meter is disconnected or giving off odd readings. Check yo codes to confirm, its really easy to do.

Update:

When the car is cold, it runs normally. Once it warms up and lowers its idle, that's when I have problems. I am no professional mechanic but to me this points to CHTS, cam position sensor, or AFM. It also tells me I need to run my codes.

codes usually not much help. chts prossible but you need to do this
Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion.
try spraying some maf cleaner in the maf