New to the bike world and a lot of the mechanical/fuel stuff is auto related and I am not sure how it differs from car to bike. But on my F4i it seems to be running rich, sluggish down low and emptying the tank faster than a keg at a frat party. Could be a couple things and runs ok above 3K, but down low it chugs a little and feels like it has random misses, maybe due to fowled plugs. But the one thing that struck me as odd is that when I take the fuel cap off it had a lot of vacuum in the tank. Enough to where on empty I could feel the tank expand back to normal size when I took the cap off and released the pressure. Bike was sitting a lot before I got it and has about 4K easy miles on it. Something simple as a clogged breather line or something more?