92 B2600i Cylinders Not Firing

I have a 92 Mazda B2600i with 180,000 miles. At present, only 2 cylinders are firing (2 & 4). I have spark at all cylinders and the compression is good. There is a strong gas smell and fuel dripping from the tailpipe, so it appears the mixture is too rich for 2 and 4 to fire. Knowing that the Mitsibushi ECM is a common problem, I checked and found it was corroded. However, after a professional repair of the ECM, the problem still exists. In accordance with the manual, the fuel injector harness resistance is correct as well. Cap, rotor, spark plugs and wires have all been replaced. Now I am wondering do I have another electrical problem or is it an issue with the injectors? Or something else? Any thoughts? Thanks, Shamus