My trx450 is letting out a small backfire right after its shutdown. The bike does not excessively backfire or pop during deceleration. The bike is a clean 2014. I put on a fmf factory4.1 with power bomb header and FCI intake with no airbox, jetting is 168 main, 42 pilot 2 and a 1/2 turns out, 55 leak. I had put a 45 pilot in when I first jetted but dropped to a 42 trying to lean up the pilot circuit becuase of this backfire. Going to put on new copper exhaust gasket and check valves. Any input would be appreciated.