88 300ZXTurbo surging when cold

The throttle sensor is only an idle contact and does very little as far as drivability. There is a temp sensor on the front of the drivers side head and a test is to try running the car with it unplugged (there is a sub-harness that has a 2 wire connector on the pass side) and see if it helps. The computer sets a fixed value on a timer from startup if there is no sensor detected and most cars run OK with it unplugged. If it runs better, replace the sensor -and- the sub-harness but the sensor is a BITCH to get to and requires a special tool to replace without removing the timing cover.

But these symptoms sound more like an AF meter that is on it's last legs. There is no good test for them other than replace with a known good unit and what kills most is a bad AIV valve leaking exhaust into the pipe just ahead of the meter. This valve has a vac can on top of an aluminum box near the meter and if you remove 2 philips head screws, you can lift up the can and inspect the inside of the valve, black carbon soot is a bad sign! This also could be the lack of power as these cars seem to get 99% of their drivability from the AF meter. Hope this helps you out. BTW I've found the codes these cars set almost never have anything to do with the problem. Like when the AF dies, it sets a code for the crank angle sensor!

No, its the AIV valve that is defective causing the soot which in turn ruins the AFM. If you replace the meter and don't replace the AIV avlve, it will take out the new meter.

Look at the boot right in front of the AFM. You'll see a 90 degree fitting going into that rubber boot with a 'heater hose' sized hose conected to it. Follow that hose and you'll find the AIV valve. On the top of that aluminum vlave assembly you'll see the vac diaphram I was talking about. This is for any US spec car.

With a known good one or a used one?

Could be the sensor & sub harness still? Seen several of these older Z's have issues with the main wiring harness as well as flakey computers. Have you tested the O2 sensor? Again these cars normally run fine with them unplugged which can help figure out if that is part of the problem. Some of those older Z's can be a nightmare to straighten out. I'm surprized the AFM didn't help at all. Good luck.