1992 GMC Safari Fuel problem

Engine Mechanical problem
1992 GMC Safari 6 cyl Two Wheel Drive Automatic

Have a 92 Safari and it has a sputtering quitting engine. Tested the fuel pressure at the test port and have 59lbs. Replaced fuel filter. Engine will start but as it warms up it seems to lack fuel. It sputters and coughs, often popping out intake. Once acceleration starts engine will smooth out and stay at a rev. Once you let it go to an idle, it often dies and won't restart. You let it set an hour and it will restart and go through the same warm up etc. And quit again. I used some Cheveron fuel injection cleaner and it now will idle forever, but still sputteres and cough when first accelerated while warm and then irons out at a high rpm.. Any ideas before I have to pull the intake? Its a day long job ++ by the looks as it falls directly under firewall in this model van.