All fuel tank venting is controlled by the fuel cap (or gas hole plug if you prefer). The fuel cap is surprisingly complicated and even more surprisingly not all that expensive, at least not for the sheer number of parts included. You (or the dealer) will have to take the lock cylinder out of the old fuel cap and swap it into the new one so that the same key still fits everything on the bike. If the bike is still under warranty, this issue should be covered- at least it was on mine.
Even Kirby is amazed at the number of parts and he is hard to impress:
Brian
Yea, that would be a vacuum issue not pressure.
I'll give the dealer a call.
Thanks