My '90B2600I 2wd recently suffers from lack of power and stalls when you first start it. After that it starts fine. Its runs smooth but my mpg has dropped 5 mpg. I've replace the O2 sensor, Checked vac @ 17.5 steady, Compression 1+4@180 psi 2+3 @ 160<> . Oil in the cylinder didn't raise compresion. Checked timing @ 6 btdc, Fuel pressure @ 40 psi running and holds psi after turned off. Replaced cap, rotor, plugs, wires, fuel filter. I beleive the MAF is good I unpluged it will running and it ran terrible. I'm not sure if the ecu/ecm has trouble codes. I don't even know if they make a code scanner for this model or where to plug it in. PleaseHELP I'm totally out of ideals.