600 shift throttle lag

hey guys, you may have seen my other posts with more details on my sled but it's a 2010 IQ shift 600 ( fuel injected). When I am coasting or slowing down and rev the throttle it has about a 1-2 second lag/ bog if I keep on the throttle it clears up. I have cleaned the power valves and replaced all the broken parts. I have tried the stock can and aftermarket. I run premium gas and Polaris VES gold oil and have tried the ethanol wires in both positions, and nothing has helped. Scuffed cylinder or busted reed maybe? there are no other signs that something is wrong. I did have one spell where it would bog out at full throttle once in a while but after thawing it out, putting isopropyl in the gas, and unplugging the ethanol wires (to richen the mixture) it ran fine after. I don't know what to do next. if possible I would like to keep the engine together but I don't want to cause further damage.

Any ideas????????:dunno:

600 shift throttle lag