I don't think there is a big improvement in trying to increase power by what you can read about for products online, cams, etc. But to each his own. The 200 is quite capable, i wouldnt worry about having enough power to get a deer out, i have hauled everything from concrete blocks to firewood with my 200ES, never an issue.
As for the K&N, i wouldn't... Your better off with the stock style filter with foam sock over it. Its breathes plenty well with that setup. Going to the K&N will only slightly increase airflow, but along with it the dirt flow as well!! LOL
I have seen the dirt ingestion caused by a K&N, its not pretty...
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1984 Honda ATC200ES "Big Red"
1982 ATC200E "Hondie"
1988 TRX300FW "Project Quad" Still in progress....