Engine falls on its face with throttle body closed, has absolutely no power when cold

Howdy y'all. I'm sorry if this is a lot to read but I've laid out all the details i can to try to find some answers. After having hard cold starts and high idling in my 85 Z31 for awhile, I replaced the tube running from the MAF to the throttle body because mine had a tear in it, and now I have more issues, haha.

Before I replaced it the car would be hard to start when cold and the engine would noticeably shake for a second when it started (IE not firing right for a second or two.) The car would idle fast, then drop lower usually to 500-600 and act llike stalling, slowly warming up to around 800. If I tried to drive the car like this it would act like it has absolutely no power, revving way higher and out of proportion to what you'd expect the car to be moving. I would have to wait until it "warmed up" and the idle picked up to 900-1000 and would drive OK. It would keep 900-1000 no matter if the lights/AC was on/off.

At first, after replacing the big air tube and the smaller tubes (PCV, etc) that run off it, and pulled the ECM fuse, the car took a few seconds to start but started right up to 900, then quickly idled down to 700, just like it's supposed to. I couldn't believe that so I tried to drive it immediately and it did the same thing, drove with high revs putting out no power. If you keep driving like this eventually the engine hits that "warm up" point and it's like the engine gets "unblocked" and it'll drive normal, but idle around the 900-1000 or even 1100-1200.

It's always done the no power when cold thing, but after fixing the leak in the tube it's doing new things. With the throttle body closed and engine braking, the engine acts the same way, like it's "blocked" or something.If you let off the accelerator and push the clutch in, the engine acts like it's laboring and then with the clutch in it falls on its face roughly down to 1000-1200rpm. If you keep the throttle even a little bit open while engine braking or pushing the clutch in, it's fine and smooth, but with the throttle fully closed it acts up. Sometimes if you engine brake with the throttle fully closed, it'll brake smooth and you can push the clutch in and it'll drop the rpms smooth, sometimes you'll engine brake and it'll be smooth, cut into that rough labored braking, then cut back into smooth, etc. Some kind of fuel cut off issue?

The only other new thing is sometimes at stops it'll idle hunt, usually jumping around 900-1000 no matter lights/ac on (idle up solenoid on/off). Could the solenoid be defective and could that explain the other stuff?
I had tested the MAF before with a multimeter and it met the benchmarks OK. I have replaced CHTS, plugs/wires, all vacuum hoses repaired and leaks inspected. Any insight is appreciated guys.