Code 27

I have a 1995 dodge ram 1500 with code 27 I have checked the wiring, replaced injectors and computer. What have I overlooked? I rebuilt the engine, installed it.I started the engine ran it about 1600 rpm about 2 mins and it burned out he auto shutdown relay.I replaced the relay, started the engine ran it about 20 mins then drove it about a quarter mile and the check engine light came on, I got a 27.I have checked the wiring by looking at it, ohmmeter, and noids. All the grounds are connected and clean.I have checked the distributor orientation and replaced the crank sensor.I have checked this truck so many times that I have wore the hood out.I need my truck, can you help?