Has this independent Guzzi man done any work on your bike yet?
If not it might be worth asking a few pertinent questions before allowing him near it. Ask him how to make the idle speed lower? Don't let him show you but if he says "Just turn that screw out a bit." Say "Thanks" and run away as fast as humanly possible.
If he has laid hands upon it just check the air bleeds on the throttle bodies. If they are both open? Once again, run screaming into the night!