1991 Chevy Camaro 1991 Camaro runs very rough

My 1991 camaro rs 5.0 tbi carburated when I turn it on it turns on fine motor runs smooth as soon as I put it on drive and give it gas it might run very rough or hesitate to pick up it my not run at all when I give it gas and something might pop under car like a fart or it may run ok at times but most of the time is running rough on the street sometimes it has made a noise in the bottom of the car like if it farts like if somtimes pops it runs perfect in the highway at highspeeds. I have replaced the waterpump, gaspump, radiator, full tune up, and took the catylic converter out and put a straight pipe out I really dont know what else to replace might be a sensor or a injector please help this is frustrating I will appreciate it.