what happens if you try to floor it, or give it alot of gas? does it hesitate and feel like sluggish? kinda julting? if it does, then you might have a bad cylinder coil, have your spark plugs and cylinder coils checked out. I had the same problem on my car around 60k miles...I changed out all my cylider coils just b/c its better to do them all at once, not that expensive if you do it yourself. And as for the fuel injector cleaner, it is VERY recommended to use it the same time you change your oil, that way you keep track of how often you put it in. Doing it too often isnt good. I have always used Lucas, or Lucus, fuel injector cleaner, dont know how its spelled but thats what it is. Every 3000 miles along with the oil change. And about the gas tank issue, it is also possible you might have gotten some water in your gas (bad gas) and there is treatment to buy for that, ask any local automotive store for it (discount, autozone etc.) Just poor it into your gas tank. I've had that happen before too. That could be another thing to try in case you havnt solved any of the problems yet. But actually what happend to me, I had problems like you are saying with my car, and I tried all those things, but found out it was the cylinder coils and they go bad after about 70k miles, but mine went out early i guess. Not a big deal, but just thought I'd let you know and see if that helps.