I currently have the same problem. I have 9500 miles on my 2018 Sidewinder. When in the Gaspe last week, it started surging and would not go over 35 to 40 MPH. Got to a Yamaha dealer in Pabos, QC. They replaced the fuel pump as they said they ran into this before. Since then, with the new pump, I cannot let the tank get below the 90 mile level, about the 1/3 mentioned here. This is not acceptable as the tank is only 9 gallons. It quits going downhill after it backfires, then starts up right away, and runs until a curve or downhill or following a group of sleds ahead of me and I have to go 20 MPH. I have taken out the pump and sending unit and put pinch clamps on the filters to keep them flat and not twisted, then repositioned them in the tank. I will mention to my dealer about the return line and tank vent check valve.