When I purchased my 2015 TG last October, it only had 5000 miles on it. I was not sure how the bike had been stored or used so I put a few oz. of Seafoam in the tank on each fill up until the the bottle was gone. I have noticed that now I am not getting the mileage I did when I was adding the Seafoam. It seems to be a few miles per gallon but after 5 gallons it is the difference between a 1/4 tank left and an 1/8 of a tank left. It is a 103 with a non-restrictive intake and pipes and a custom map from a VH Fuel Pak 3 for the pipes. No other engine mods that I know of.