Ecm or chip problem?

['71buickg.s.]

We had been having problems with what we thought was the fuel pump until a friend came over and we discovered it was the ecm, he happened to have a spare so it gets swapped for the bad one. We take it out tonight and it seemed to be running on its own so to speak.. it seemed like marty was stabbing the throttle but he wasnt, and every time it let out, the check engine light would flash.. this worries me. Is it the ecm or what?


TIA
Josh

there never seems to be a place for our specific problems!