Alot of great info here. I had a similar problem. My 2011 RTS Sm5 would run great on full tank of gas, but once it got down to below half and I stopped for awhile. Mine would start and run rough, twist the throttle and it would barely run. Most times it would stall. It would work out of problem if i could get started down the road. Any way it was my purge valve. Has run great ever since. Bruce