You may very well have another issue, but just draining the tank after 11 years isn't enough, IMO. When I bought mine, my wife and I dropped the tank, drained it, poured a little mineral spirits in there, threw a couple small pieces of chain in the tank along with some tumbling rocks I had and shook it for all it was worth, lol. We then repeated the process, you'd be amazed at the gunk we got of the inside. Rinsed it real good with water and let it dry for several days before putting it back under the car.
The tank was in great shape otherwise, so I elected to try that before replacing it.
I might suggest pulling the fuel filter and replacing it.