89 chevy 2500 5.7L

I have this truck that wants to die under light acceleration mostly in reverse(backing out of a parking stall) it was doing odd things when i first got it it would set a code 43 and 42 injectors click when it dies key on engine off when it died the computer was retarding the timing on my scan tool and at one time it idled way high and i could not communicate with the ECM so I repaced the ECM and PROM (that has been updated several times according to GM) now it does not set the codes but it still falls on its face under light load but i see no data parameters that catch my attention to being out of spec stumped on this one any help i would greatly appreciate thanks