1990 b2600i not running

I am about at wits end. I own a 1990 b2600i and it has been great since 1998 when I bought it. Until now. The problem started as an intermittent one where while driving, the vehicle would start to lurch and lose power, sometimens die altogether. Upon starting it again, engine RPM would not go above 1500 RPM, any further depressing of the accelerator would cause the engine to die out. After a while, the problem would clear up and I could drive again, temporarily. The intermittent problem continued. I did all the routine stuff, changed cap, rotor, plugs, air filter, plug wires, fuel filter, PCV valve and the problem persisted. Next thing changed out was the fuel pump and the associated cutout relay. After doing all of this started the vehicle. Again, would not go above 1500 RPM. Reset FAILSAFE mode and engine ran great for about 2 minutes then fell back into failsafe mode. Tried to reset the failsafe again and now the engine doesn't want to start at all. Also, I cannot get the malfunction code to flash for me. The local shops all have the OBD2 type analyzer and the connections do not match my terminals so I am trying to jumper the test terminals to flash the service engine light. Can you help?