just died

driving this morning fine , stopped at light and it died. no start - let sit for while , started for 10 sec. or less then died. turns over great , have spark , good pressure , new fuel filter , spayed choke cleaner in the butterfly and fired up , can rev engine but let it idle and it dies and wont restart w/o choke cleaner in the butterfly --- no codes either
please with some ideas --- sorry 1922 4.3 W vortec close to 200,000 miles still getting 16 mpg in town.
SUNDAY - 10 hours and $500 later still having to prime to get started. replaced fuel pump, had ignition mod. checked(was fine) , finally replaced spider ass. and no change in the problems. fuel pressure 60 then goes to 52 and builds up to 58 and holds. i am at a loss - someone please help . was told by mechanic that sensors werent the culprit?!
alot of people look i see but noone has ANY solutions or ideas?

replaced ECM, IAC , checked MAP sensor(ok) ,new temp sensor - so now it goes to the garage - when i find out i will post so others dont drop that kinda change on guess'

garage is thinking the timing chain may have loosened and jumped a cog or so?

Check the power brake vacuum hose.
The Manifold Absolute Pressure and Throttle Position sensors are also suspect.
What year Bravada are you refering to?

if you just replaced the fuel filter it is posible that it is on backwards witch could reduce the flow. make sure that the arrow on the filter is pointing to the front of the car.

I guess the idle air control valve could be stuck completely closed or completely blocked with sludge which would keep any idle air from getting in the motor.