Hi. I have the 660 Rhino and thinking of buying this high volume intake kit from Rhino Outfitters.  I think it's really cool. It says it adds 2.5 hp and 8 ft/lbs of torque. Kit includes 41mm FCR style carburetor, Custom formed intake tube, High volume air filter, Outerwears pre-filter, Custom throttle cable. This shop has lot's of useful stuff for your Rhino, check it out.