my car dies when i come to a stop on 1991 Toyota MR2

I just perched a new Mr2 i put a jdm ECU in but didn't start so i put the original ECU back and it started up but then it died when i gave a little burst of gas. so i checked the alternator and it was bad. I replaced it and started her up went around the block and it died at the first stop sign. can any one help!?

Asked by for the 1991 Toyota MR2
does she crank when you try starting? if it does than could be fuel pump. test fuel pump manually by turning ignition key and stopping before it cranks. you should be able to hear the pump priming. a short whirring sound. if no sound than it is the pump.