Re: deceleration back fire
popping on deceleration is a sign of running lean. There are two possible causes:
1) If you have reburn emissions controls, when you decelerate, air gets pulled into the exhaust and allows the unburned fuel (however little) to reignite. Can also happen with exhaust leaks, but that's less common.
2) The more common cause is that reducing the backpressure has changed the intake draw in your carb and you are running lean because of it. If you can, try applying "a little" choke and decelerate. If the popping goes away, it's time to rejet. The fact that the factory pipes to NOT pop is a good clue that this is the problem.
Since you have a more recent bike (my experience is from OLD bikes), you might also be able to adjust the electronic ignition using "Power Commander" (IIRC) to adjust the performance parameters.
Regardless, you are probably experiencing an slightly over-lean condition. Getting more gas into the fuel-air mixture is the most likely solution.