Like everyone else is saying, Techron is good stuff - just be sure to get the actual Techron concentrate, and not the Pro Guard stuff that's cheaper.
You might also want to try Gumout Regane Complete Fuel System Cleaner (Gumout has a few products - look for the one with this specific name - it's a clear bottle and the fluid is yellow). You can get it for free after rebate at Advance Auto Parts until 4/1.