Someone please explain what happened?!

a few months ago i posted that my 15′ 800 xmr with k&n air filter and go deep snorkels, wasn’t getting top speed of 64-65mph any more. Members suggested the belt, so i changed it, didn’t make difference but i hardly ever ride that fast so i said what ever.

Saturday i rode, mud and trails for a few hours then got on the road to get gas, so i opened her up, throttle pined all i got was 54mph – 6000rpm. i kept the throttle pined cuz i was on the rode. the all of a sudden i heard the rams come up and the bike like took off, bam 64mph. got to a red light b4 the gas station, waited for green then walked the throttle and she took off like a bat outta hell, hasn’t had that throttle response since it was new.

when i got to the gas station i walked around the bike and knoticed the exhaust was a tad louder, more of a deeper sound. could she have blown something in the muffler? my friends think it may have just had crud in it and it finally blew out but im not sure.