I hope you don't mind, but we're all gonna be bonding with your Guzzi now!
" . . . you can hear air . . ." makes me think you should look for intake or exhaust leaks on the left. It's not uncommon for the rubber intake to slip off and give trouble like you describe. Otherwise, it could simply be time for a full tune-up from valves and TPS and spark plugs through throttle body balance,