Deedee

I have a 98 k3500 5.7 V8 chevy pickupThe truck was running perfect and then we went to are storage unit to drop some stuff off and when I came out and the truck wouldn't start it will start up then die. Start up and die I have now replaced fuel pump, fuel pump relay,fuel filter,plugs, wires,idle air control valve,cleaned the fuel pressure regulator. And still the same issue.. I had a friend stop by who brought over a pcm from a 96 and we put it in my truck and it started right up except now straight fuel was coming out my exhaust and the check engine light is blinking. Issues I've never had before with the truck I just read about security lockout and wonder if that is what the original issue with my truck was but the only thing is my security light was on for days before this all happened but it went off and has stayed off