i got the same broblem .did u ever fix it if so would u plz let me know im pulling my hair out

 

Try HPD Jet Kit #CK5S

 

check your exhaust for anyh leaks!! And I mean any... even a small one will allow air into the exhaust system and this will back fire when you back of the throttle..I had the same problem. I found the front gasket (donut type near the head pipe... I HOPE THIS HELPS everyone.....