1992 trooper fuel or sensor problems

Can anyone help with this one? I am working on an Isuzu trooper 1992 with the 3.2 L DOHC V6 . It Will only run at idle. as soon as you apply the throttle it stumbles and wants to stall . After running for 2 minutes this gets worse to the point where you cannot give any throttle at all or can only achieve 10 mph if you feather the throttle. There are no stored codes in the computer. I checked the timing belt and it is correctly timed. I have also renewed the fuel pump and tank sendig unit recently. I disconnected the exhaust ahead of the catalytic converter thinking maybe it was plugged . This failed to change anything. I could go ahead and change the TPS THe 02 and all the engine management sensors at major expen$e but am unconvinced this would help. Please reply if you have had a similar case or have any advice to offer. P.S Am unable to locate the fuel pressure test connector to do a live test with the engine running. Any help would be greatly appreciated thank you.