Did you drive with the maf sensor unhooked? If not, please give it a few moments to learn and give that a try. A faulty maf can cause these symptoms.

Just to clarify, you cleaned the IAC and the passage where it sits, checked for vacuum and looked for a fwe other things. And the car got worse after the mechanic did the gaskets?

Cleaned IAC and seat/ports- Check
Cleaned and ran both with and w/o MAF plugged in - check - no difference
Pulled PCV valve, cleaned checks out good
I have not put my vac tool on any lines but have moved pulled and flexed on the vac lines and can't find anything of concern there. Problem is so intermittent.
*read through Dans' diagnostics last nite and looked through all the test procedures- Sorry guys, I didn't know all that was on here- From what I'm gathering I'm down

It was going downhill before the gasket job. I don't feel that work has any relation to current issues.

Drove in to work this morning- not so much as a sputter- ran like a perfectly tuned Rolex- 20 miles on cruise with 2 stop lights.
Going over to station across the street and have him scan it and see if there'* anything he can pick up.

It'* seriously making me ill.

What you have here is an intermittant issue. Very tough on the diagnosis. It might be as simple as the IAC not working sometimes. Maybe a chaffed wire on the harness.

The mechanic is the best way, he'll need to know what to expect to see and when the issue happens, he can reply the data to get at which item appears to have been out of spec.

I worked on a GTX a while back with a intermitent MAF problem. Turned out to be a loose connection in the wiring harness at the MAF plug. Tightened the pin on the wire and problem was gone. Mas a MAJOR pain to find.

I'm about down to loose wire somewhere too. today at noon drove in to inner city traffic- tried to die on me once but was watching tach for the signs. I know when it'* going to do it if it does. Drove home- nothing, all normal. Didn't have time to get it scanned.

I did notice something though- I've been out looking at the wires and connectors closely and I notice a vac line off- or should I say a nipple with no hose, no cap. Center of attached pic.

That'* nothing, just a breather.

Check for spark plug wires touching the wiring harness or the injector wires.

That breather should have a filter though. You can pick one up at rock auto (ACDELCO Part # 21913), and use a discount code from here https://www.gmforum.com/general-gm-chat-88/rockauto-discount-code-279335/

I've worked on seperating wires looking for rubs and loose connections. One summation, this strikes me as a poorly engineered harness design and routing. Unless someone has goofed it all up, I can't believe how sloppy it is with overlaps and wrapping/stuffing in and around. It seems to be laying all over the hottest stuff under the hood aside form the exhaust. I need to replace a lot of loom covering that'* all brittle and broken.

I dunno- play it as it goes.

This situation seems to be as variable as the weather. 2 days ago- ran pretty good- yesterday, going in to work, perfect. Coming home, not so good. yesterday, even warmer out- upper 70s- going badly again. I start moving wires around trying to make a difference, made none.
Today, warmed up to 80, running badly. Noon time, I had to power-brake it everywhere to keep it running. I slowed from about 55 down to 35, car stalled going straight ahead at about 45 (first time this has happened going this fast)- mind you it'* always while I have no accelerator input when it'* trying to stall. Cruising at 55 if I let off I see tach drop down to about 1500 then drops like a rock bouncing around 500 rpm- mind you I'm running 45 by now and the motor is barely running- like pulling the AIC control out. I hit the pedal to keep it running and I get a huge lag but finally it starts to rev and clean up and again- runs like a watch. It may do it and it may not do it.

Would it be a bad idea to replace the AIC control so I could eliminate it at least? I don't even know how expensive they are.

Have you test or changed your TPS?