INFO TO FOLLOW IS A PERSONAL CONTRIBUTION FROM MONKERZ
If you are having backfire problems on deceleration, and own the 1500 Fi series motor with after market exhaust pipes this cure might be just what you're looking for. Before spending the money and effort on coasters try this quick cure. It worked for me on my 1500 Classic Fi with Vance & Hines Straight Shots. Got this great tidbit from Fergy, VROC #6588.
*NOTE*-Do this at your own risk, I make no claim that it will cure your problem nor affect gas mileage either plus or minus. I can say it cured my backfire and over 5K miles has created zero problems. From what I understand this is caused by a re-intake pipe to feed unburned exhaust back into your intake mixture (EPA crap). The backfire occurs because it is mixing this mess with your regular fuel flow.
Here is the poop on this fix. The only parts/tools you will need is a wine cork, a knife to whittle it down and a wrench to remove the right side air cover. First take the chrome air cover off to expose the fuel intake system. You should see the picture below.
Next, slide off the item above in the picture (ISC valve, idle speed control). This will expose the pipe you will block with the cork. (SEE NEXT PICTURE)
Now take the wine cork and whittle it down so it securely blocks off the pipe in the picture above. Put everything back together and give it a try. This cured my problem 100% and hope it will do the same for you. Good luck! MONKERZ.