So I have an 87 ae86 with a 20v blacktop swap I'm running the stock compooper and stock coil and igniter on 1zz COP conversion and I keep having issues when the car is cold I can't rev beyond 3000 without mass miss fire and no power and the tach bottoms out until I get back under 3000 rpm but after about 30 to 60 min the problem goes away!? Is it a grounding problem or something like that? That's for any help you can give

Was the wire harness self built? Or purchase .. Sound like wiring peoblem
I would check all the plug make sure they are tight and connected . Try a different set of cop try 1nz
I heard some got better luck with them.