A. My answer is yes, but don't overdo the amount or use it too frequently to be on the safe side. My recommendation is to use Sea Foam^®, an effective, but mild additive. I doubt very much that the fuel additive caused your FZ750 engine to blow.
Comment: The answer to this is somewhat controversial in the Virago Tech forum. 9 out of 10 will say yes, and offer personal experience to support their answer.  I have used 'Iso-HEET^®' by Gold Eagle, to remove water from my gas, and I have used 'Sea Foam' with every tank since both bikes were purchased with no ill effects. Most people report no problems, but a few have said that they have heard of someone who did. My opinion on that is, problems when an additive were used in a Virago are probably just urban legend. 'Sea Foam' and most other additive manufacturers list motorcycles on their containers and/or claim they are safe for all engines.