Sounds a lot like a coil problem I had on a Grand Prix years ago. Here is some info on checking the coils.

Joel

Part 1 -How to Test the Ignition Coil Packs (GM 3.1L, 3.4L)

Guys, you're sorta talking greek with these codes. The MAF sensor in this car is almost new. But I guess I can unplug it and see what happens. I watched a video on Fuel Pressure Regs failing. And it seems similar. So going to look into that as well.

Is this the video you watched on testing the fuel pressure regulator?

The relevant part starts around the 1:50 sec mark

obd 1 code retrieval.

https://www.gmforum.com/specificatio...cks-**-278820/

The are new MAF sensors, and there are new MAF sensors......most are rebuilt, and if non OEM, are known for failure right out of the box, or even just a few days or weeks.....

Tech 11 is correct=do that = then check all specs on map & tpssensors- its going in open loop ( no computer ) -reason why its running badly! thats caused bt a sensor problem!! Did u have the battery disconnected @ anytime before it was running good last time reported??

it obd-1 system -i have a scanner for that & many times theyre avail. from older mechanicx on craigs list! best to learn how to get obd1 codes & read them -- go here to learn-

http://www.aa1car.com/library.htm

Latest & NO SO greatest:
1. Disco'd MAF Sensor, ran even worse
2. Replace all coils, plugs and wires, no help
3. Checked the Fuel Pressure valve for failures, several times, looks good.
What I am not getting here, is the intermittence. I drove 25 miles the other day, the SES light even went out a couple of times. Then BOOM! right into the stalling/misfiring mode. Just today when I replaced the plugs and wires, ran great for 15 mins, then Boom!
My gut tells me I am looking at a fuel issue here. But again, I don't get why that would come and go.

1. read flash codes

2. do coil output check when the vehicle acts up with an ST-125.....

I just found a link on the flash codes. So I will give that a try.
(BUT) I wanna ask about the possibility of vacuum leaks. Because the other night I was fiddling around with vac lines and the car mysteriously ran fine. I also noticed the vacuum tree which comes off the manifold moves. Is this normal?

You can spray carb cleaner on the intake gaskets, vac lines, etc. to see if there is a change in idle....