Get the piston rings checked. They tend to flake or chip on the intake side (compression test will show good numbers still). We re-ringed 2 800's recently after going replacing injectors,various different sparkplugs,etc.
Get the cylinder pulled off and check the rings, they will most likely have chipped or pitted on the intake side(compression test will show a good reading). Recently found this on a 2011 & a 2012 model. Polaris is no help (their answer is always to check fuel,fuel resistor, sparkplug caps/deny...