Ok here is the deal: 2006 Rhino 660, Blackrhino CDI, Looney Tuned Exhaust, K&N, Electric fuel pump, stock clutch. Ran great until now!!! I am having a terrible "popping" at mid-high rpm (about 5000-6000rpm). SO I adjusted the valves, cleaned the carb. and replaced a couple o-rings, replaced the...