If I'm in the wrong forum, my apologies... I'll move if needed.

Long time reader, first time poster here. Just like the title says, I have an LS1 swapped Firebird that is extremely hard to start, and stumbles/dies at idle after a few seconds.

Before anyone asks, yes I have searched extensively on this, and googled every combination of words that I could think of to try and find a fix..................

Short version of the story:

Swapped an LS1 in my '99 automatic v6 bird late last year. It drove perfectly fine for roughly 400-ish miles, then it started showing some problems. At first, it would quickly die the first time I'd start it, then start up and run fine immediately after that. It did that for 4-5 weeks, then one day on my way to work (5-6 mile drive) it died 3-4 times when I would stop, and then another 2-3 times on the way back to the house. I parked her so I could start troubleshooting. I discovered that I had a small leak in my fuel line, and I was running about 95 PSI at the fuel rails, so I rebuilt my fuel system (all new lines, fuel pump and Corvette regulator/filter) and am now running 58 PSI at idle. Now, the problem is that it is very hard to start the car (anywhere from 5-8 tries before any real sign of life), and the times that it does start, it idles extremely rough, stumbles and dies after 10-15 seconds tops. If I get on the throttle a little bit when it's idling, and take it to about 2K and hold, it runs fine, but will then dies as soon as I let off. This is all while the trans is in park. Exhaust smells like it's running rich as well. Here are the mods I've done so far, and what I've checked/swapped as of right now:

Mods
- 3" long tube headers, true duals dumped at rear axle (No CATS)
- AIR/EGR/Rear O2 deletes
- Ported TB
- Changed to Bosch 13111 O2 sensors to avoid using O2 sensor harness extensions
- LS6 PCV/Valley cover swap

Checked/Swapped
- Cam Sensor swapped
- TPS and IAC swapped
- MAF Swapped
- Did VATS resistor bypass to rule out bad key/tumbler
- Ohmed all pins at ECU to check for pinched/grounded wires
- visually and continuity checked all sensor wires/connectors
- swapped plugs and wires
-capped off HVAC and EVAP from intake as well as replaced gaskets to rule out vacuum leak

I've had my ECU mail order tuned twice, once to do all the deletes, and a second time by someone else to see if a bad tune was causing this problem. Second tuner insisted that the first tune looked good, but reflashed the ECU with his version of the tune, no change. I'm up against a brick wall, and am hoping someone has some advise on what to look at since I'm out of ideas. Really hoping I'm not overlooking something completely obvious, but I'm seriously trying to avoid taking her to a mechanic as I would much rather fix her myself. Definitely appreciate any help/ideas as I really miss driving her, and am seriously tired of throwing parts at her and hoping it fixes it! Thanks!

EDIT: I've done the TPS/IAC relearn steps w/ no change. Disconnected the MAF, won't start. Tried unhooking IAC and starting, and it'll idle REALLY badly, and constantly surge/stumble between 600-1K RPMs for minute or two before I shut it off, and will go back to original issue when plugged back in (both old and new IAC do this).