It looks like one of the rubber stops that you remove when you pull the airbox and install the Freak kit. As long as it isn't one of the bump stops for the gas tank I wouldn't worry about it.

2006 865 Neon Blue/Jet Black Speedmaster,790cams, TTP Stage 2 Firestarter, Epco Exhaust with 10.25" Samson Vrod baffles, UNI pods with 40 pilots, 150 mains,Thruxton needles, 3 turns out.