91 240 Stalling. Many tests completed what to test next?

[Jpawww]

My 240 started stalling as wi as pulling away from lights after 30 min of driving. It has gotten progressing worse. Now I can't even make 10. If I sit and let it cool for a bit was 15-20 min I could then restart and get enough run time to get to my destination. It will always start and run for a small period of time. But it's getting frustrating
I have done the following:
-Replaced the fuel pump relay. It still gets warm on one side, but swapping it out during a spell does not fix the problem
-Replaced the fuel filter. 3 years old. See history below.
-Removed and cleaned functional flame trap
-Tested the fuel pumps,
--The lift pump will lift copious fuel quickly when disconnected from the main and main power was disconnected. 3 years old see history
--The main pump tested to put out 35-38 psi under normal operation and when it starts to stall the pressure goes up to around 50 psi. 3 years old see history
-Tested and replaced the the O2 sensor which was producing no voltage when removed and heated with a propane blow torch as described in another similar post. This initially produced better run times until yesterday when I arrived at the muffler shop.
--I started the car with no O2 sensor and a large cloud of dust blew out. And drove it home ~20 min without problem, at night.
--also used this opportunity to replace the exhaust manifold to exhaust pipe gasket and tighten the bolts to spec, had been loose since self weld to repair broke. Welds to catalytic converter. See history
-Catalytic converter (replaced in Sept-12) was cut down in the shop and visually inspected by the profession who said that it was still in warranty and had it needed it would have been replaced.
--Upon arrival to this shop I couldn't even keep in running. After waiting It started behaving for the quick move.
--Later found out from another mechanic friend that this shop was known to be cheap and crooked. IE didn't even suggest to have my mufflers replaced when I had the converter replaced. Is this necessary and normal to not replace the mufflers at the same time?
-Ran DTM1 codes returned with: (instructions from Brickboard.com for testing OBD1)
--O2 sensor(232 212) missing or intermittent, obvious since I drove home without it.
-Ran DTM2 System senor signal test: code returned with:
--RPM sensor(214) missing or intermittent
--not able to get 3-3-3
--all other sensors got OK report: had to start the car to get 1-2-4(Engine idle compensation for automatic transmission
-Ran DTM3
--No codes returned able to hear 4-5 components activate and match the blinking light before hearing the same component activate again.
-Cleaned and replaced all fuses related to engine and management.
-AMM: car runs worse when not connected and is just as likely to stall whether connected or not.
-Tested for intake leaks using spray carb cleaner around intake points. The theory being that had a leak been present the idle would have revved.

History
Had similar problems in 2010 fixed with replacement of fuel pumps, fuel pressure regulator, flame trap, vacuum hoses, Cleaning throttle body.
2010 front seal and timing belt
2011 starting to have problems and came across a 2 month old reman AMM in junk yard and installed to relive problems. Also replaced catalytic converter to meet emissions. Also air cleaner heater hose, rotor cap, wire set and rotor.
2012 had a small fender bender which deployed the air bag. Required replacement of all engine mounts, transmission mounts, carrier bearing, side front bumper supports, neutral safety switch, windshield(my hand impacted), and rear bumper(whole assembly +rear body work)
Currently water pump is leaking but I'm only having to add 20 oz every 160-180 miles(every other week). Leak is between block and pump.
Semi related the welds failed on the catalytic converter so I dropped the exhaust pipe and rewarded it. drive for 3-5 months (winter) without significant problems.

Currently cannot even run 15 minutes at night with out stalling on the road. Can reproduce by idling for 10-15 min or driving 10 min and then sitting at a light in drive. The finally thing to make it stall quickly is while in drive goose the pedal a little(not a corresponding amount of acceleration is created) and ten it will stall on the second or third goose. I can always seem to comfort the engine and keep it at least idling if I throw it in neutral or park, but when in drive or reverse it is likely to stall when fuel is applied. Sometimes I can limp along if I only allow it to idle, but eventually this even fails.

All this to say that I'm frustrated and don't know what to test next. I've done everything I can think of... But I know y'all will come up with something.

[wagonlove940]

I'm having the same issue I saw a fix on YouTube today someone fixes by replacing the intake manifold gasket. I see this was years ago hopefully your problem is fixed. If anyone else is curious the video is here