My new 2008 outlaw backfires when I let off the gas.
This has done this from day 1. The dealer noticed this when they put gas in it for the first time. They have checked the valves and the sparg plug gap. Both are OK.
Has anyone else had this problem?  

Yes, I have tried sealing exhaust joint and headers with no luck.  Polaris dealer will not work on it under warranty.  Local mechanic suggests that it is a pilot jet or air screw problem.  I don't think you can get to the air screw without drilling which might void the warranty - so, I'm still stuck with the backfiring.  Have you found a solution yet?  

I change my pilot jet to a 50 no backfire it will not void your warranty changing it  

It is most likely an issue with the head pipe sealing at the manifold