Hey guys newbie here. Have a question. I bought a 2007 m1000 and the guy I bought it from replace the engine and didn't finish it. I finished runs good but at about 4800 rpm its starts to backfire out the exhaust. I Ckd and ohmed all the sensors all good. Has no engine light on. I hooked up a timming light and when it backfires the ignition does not miss a beat. Tried a new stater didn't help. Found it had the wrong injectors replaced them and didn't help. Ckd the reverse switch and the throttle switch. Pulled the tank off and ckd for rubbed wires and Ckd all the wiring. Not sure where to go next . Anybody else run into this. Any ideas thanks