Now, back to your situation:
E15 is required to have a warning disclaimer at the pump. I would definitely avoid any pump with that label. IF the E15 actually represented the exact mixture of that particular blend (and it certainly varies), you were running on the edge of what could be expected to yield satisfactory performance in a non-flex fuel vehicle. That also means roughly that same 15% of whatever volume was in your tank could absorb close to that same volume of water( although the actual "mixed yield" would supposedly be slightly less. You then added more water absorbing liquids, so you may have ended up with a less-than satisfactory motor fuel. This immense amount of miscible solvents will certainly strip any varnish or other build-ups. If you have been running E10 for some miles, what you discovered may be the most of it. Assuming the vehicle continues to run with no major glitches, I am not sure I would hurry to change out the carb. Once you are certain most contaminates are either gone or well-lodged, then change carbs. Just be sure the rebuild is alcohol resistant. If MN regulations do tighten up; you may want to look into the exempt "collector vehicle" classification to reduce the potential for future problems. That won't solve any local availability issues, but you may be able to at least find local fueling with lower amounts of oxygenates,such as some "reformulated" fuels.
Paul
