Vehicle hesitation, does this sound like its caused by watered down fuel or another problem?

ok so for the past few days while driving my 02 trans am I have noticed that I’d be stepping on the gas and all of a sudden i would feel a sudden loss of power, kind of like te car was chugging along for a bit, then the horsepower would kick in, also to add in within the last 2 months I’ve heard while idling, I’ve heard a rattling sound in the exhaust, now does anyone have any idea what this may be, because tonight while I was driving i had the same sudden loss in power, while driving i felt the power loss so i pushed the gas in harder and noticed that the car was still slowing down so i down shifted to 1st gear then stepped on the gas again and all of a sudden the power was back, does this sound like a case of gas that has too much water in it or could this be something much more serious.?