So here it is, about a month later and I'm having the same issue. I only live about 5 miles from work, so I only have to fill up about once a month (which is excellent!). I noticed today that my fuel gage is slightly above 1/4 tank - pretty much the same level as last time.

So, I'm pretty sure I have some crap in my gas tank... anything that I could do to clean this out without dropping the tank? That would most likely be a pain in the ass.