2012 skidoo 800 etec slight backfire

Hey guys I have a 2012 skidoo etec 800 that started out 100 percent un modified then it blew up and I've installed a ptec cylinder in its place drilled oil ports for rave valves and have no problems with it except when I come off the throttle on wide open pulls it slightly backfires on its downrev and keeps eating reedvalves. I've been through 2 sets of reeds in the last 300 miles! Can anyone point me in the right direction? Like sticky raves causing this? I also have a tuned pipe sensor code so would that cause it? Thinking of just bypassing sensor to see but want some real thoughts from some skud gurus! Thanks in advance for the help!
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