96 Cutlass Supreem 3.4l DOHC Wont idle once it warms up

I have replaced/checked all the vaccum hoses. and checked the o2 sensors. cant find any thing on Google that can help me. I suck in many hours trying to get the ding dang car to stay on. I have replaced the computer thinking that that was the issue. sunk money and time and need help. Please help

also replaced the IAC, the ECM, lower manifold gaskets, put new plugs in it. Plugs were black and sooty, and worn. they were replaced on principle. unhooked exhaust on manifold thinking it may be the converter but that wasnt the issue.

has it been scanned? it’s a whole lot cheaper than slinging parts at it. but if you’re into throwing another part at it try a coolant temp sensor. I say the ect because it could be failing to where the pcm thinks its always cold. as your engine warms up it needs less fuel to run, and if you overfuel it when it needs to idle, it will die from lack of oxygen.