1995 Camaro 3.4 Rough Idle

Recently after sitting at a red light Iwent to take off & it seemed as if I just didn't have the power I normally did-almost felt like something was clogged. Car would let out small "backfire sounds." Also, if I let off gas some or put my foot to the floor, it would smooth out. I took it to the garage to be tested for the engine light & the code said O2 sensor was bad. 1 week later, I changed both O2 sensors & had to replace the alternator as well. Since the 02 sensor has been replaced, I notice no difference & the engine light is still on. I havent had it retested, but prior to any repairs, the o2 error code was the only code reading. I have come across several things online that others have tried, but it can get expensive changing all kinds of sensors. Any ideas?