ok, i noticed recently while i was driving (only at low rpms) my car gets an occasional hesitation when i apply some gas. it feels like my car is hickuping. it seems to be getting worse, now when i start my car, and if i rev the engine not in gear, there's like a pause, then my exhaust seems to kinda "pop" and gurgle. my car sounds kind of untuned when i rev it. a friend says it could be the gas. or the sparkplugs. the sparkplugs aren't old. i've never changed the fuel filter since i bought the car (that was 40,000 miles ago) could that be the problem? my exhaust tailpipe is shiny and there's no built up residue inside it. did i maybe suck some water in my intake?

what should i do?

Have you checked your plugs and see the condition? See if they are carboned from being way rich. My car was doing the same thing (as far as I can tell by the explanation) It was from my car running SUPER rich because the ECT sensor was unplugged. I'm not saying it's your ECT sensor but it could be something making you too rich.