91 4.3 TBI out of a S10 Blazer. I have good spark, good fuel but it will not run. Timing is set to 0 degrees(second mark on the crankshaft) . I have disconnected the timing advance wire. Fuel pump is rated at 20psi. I am getting a good cone of fuel into both injectors with some pulse/modulation. I pulled off the fuel pressure regulator last night and will replace it as it didn't look all that great. I am getting some fire back in the manifold. I can also disconnect both injectors after cranking for a bit and the motor will stumble/want to crank off the gas still left in the intake. @R Q has suggested a new MAF. Any other ideas?