New from NY

Just purchased this new to me uses 2011 Polaris Sportsman 850xp with Eps. I have one question. The quad has an aftermarket muffler and a k&n air filter on it. Apparently at one point I am assuming it had a power commander on it since it has a power commander sticker on the front but the seller says he can’t find one anywear. I know with motorcycles when you add an exhaust and intake you usually are supposed to rejetyour carb or remap your fuel on the computer with a power commander which basically tricks the computer I to thinking it needs to put out more gas.
So my question is that since this has an aftermarket exhaust and a k&n intake filter do I need to install a power commander. The seller States that it is still running a little rich. Are these aftermarket exhausts really worth it? Are they usually louder than stock? I am thinking about just buying a stock muffler and reinstalling it on the bike and getting rid of the aftermarket one. I am coming off of a 2010 Honda rancher AT 420cc so stock 850 should be more than enough power.
I already plan on installing the richochet a-arm guards and skid plates, moose front bumper, bison rear bumper, still thinking about the rack extenders and hand guards as well as a LED light bar.

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