The only thing I can add is did you get water in/on your air filter? I have done that before with my Heavy Breather and noticed problems for a while but soon went away. Just forgot to put the rain sock on.

I have read here as well as rags that leaf blowers will damage paint but I have never had an issue. But I only use it sparingly if at all there. Where it is most useful is on the engine and wheels as it will get rid of any water laid up in the heads or anywhere else. Just my opinion which is worth nothing....

As far as the backfire on deceleration, my 01 RK is not EFI and I dig the sound, especially on a long winding downhill 25 MPH road in 2nd gear, such as the ride down Pilot Mountain!!! Sounds cool to me.