Ignition coil would be the first thing to check. switch them to see if the right starts doing it. If the left keeps it up, well, the once in a while backfire is when it loads up with gas. If you have done nothing else to the bike CDI may be the cause. I went through it on my 05. Same thing, left cylinder went to sleep once in a while then just was gone.
At least you can get them cheaper than 600 bucks! when mine went down.
