cylinder drop on 1990 Mazda B2600

truck was running fine,now cylinders 2 and 4 will not fire.
I have good spark on both cylinders. Engine will run,but I
can remove plug wires and engine sound the same.apparently
I'm not getting fuel to those cylinders.Yes,the engine is fuel injected,it is the 2.6L I.

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3 answers
help--mine is doing exactly the same thing--did you get to the problems--thanks a bunch--was told yesterday that computer is bad and causung problems
I had the same problem which I corrected by having the ECU rebuilt by AVProECM.
http://www.avproecm.com/mazda.htm
Look into this problem on other forums. You'll see that this is quite common and the repair is very effective. Costs about $200.
DID U HAVE A TUNE UP DURING THE TIME BETWENE UR PROBLEMS ?