93 notch Idle problems..PLEASE HELP

I am new to forum, but not to Mustangs. Just bought a notch that runs strong and cranks fine as long as the temp is above about 40 degrees. Basiclly stock except for exhaust and The guy told me it had an aftermarket ECM but didnt know what kind cuz a previous owner had installed.It has no O2 sensors he said that they were supposed to be gone for that computer.Anyway I noticed the Tps sensor was unplugged so Iplugged it up and cranked it, it reved up to 3000 and stayed there! So I replaced thr TPS and set voltage to .98 with key on. still revs to 3000 then slowly drops to 2000 and stays. I reset the ECM in the traditional battery cable way. no luck ...I'm about to loose it. It cranks and runs fine with it un plugged

Yeah I hear ya something is not right...The only thing is it must have had a different motor in it cuz its a stock block, stock heads, no cam. But for some reason it runs like a scalded MOFO when you step on it ...It just has the starting issue. You still think I should replace the comp. The wiring harness is still all there O2 sensor wires tucked under cold air and tps sensor wire just hanging

Also My check engine light works ...But is not on !