Recently got a 2008 GS with less than 8k miles. I rode a 2010 GSA several weeks ago on a test ride, and rode a buddy's GS for a short while. But a difference I have noticed on my new GS is when I am decelerating it pops and rumbles in the exhaust. Especially coasting up to a stop in second gear. Usually a pop like a kind of backfire. I don't recall hearing about this before and I didn't experience it with the other GSs I rode. Is this something to be worried about??