I'd really take it to the dealer. IF you tinker and make it worse you'll be looking at a big bill for the 'repairs' and to rectify the actual problem. And there'll be no more warranty. Period.
Go to the dealer.
Tell them if they find nothing wrong you want the tip over valve changing. It's there as a safety thing, and I had problems with mine last year. And sounds exactly the same problems, with it sounding like the breather is pinched but it isn't.
Gina
03 America - Pretty stock - except the TBS wheel...

06 America - missing, presumed in bits. With it's TBS wheel...

09 America - It's very blue....