If anybody could help, that would be great.
Right now I have a 99 RMK. Last year, I rode by brother in laws 99 600 xc and loved it. The clutching was just perfect with a ton of acceleration at 50-65 mph and a top speed of about 110. Is there anything I can do to the clutching (without buying a new one), and if so, what, in order to get that type of performance on my RMK. Right now, I have bottom end coming out the ying yang, but top out at about 92 mph. Everything on my machine is stock. Help :(

First thing I'd do is re-gear it. I believe the gearing is quite a bit lower in a RMK. Then I'd start playing with the clutch.

Derding is right! Your gearing is low for powder so you will have to gear up. Also, in order to go fast, you will have to loose the big track, and go to a 1" or 1 1/4". Trust me. I converted my 700 XC over to a 144" 1 3/4", geared it down to an RMK and lost over 20 MPH on radar (110 down to 89). Then after that, play with clutching.

Yep, you'll have to gear it up.

As for the clutching, you'll probably need heavier weights, and a different helix.

A 1.25" track would make it feel alot more like an XC too.

I believe it has 19-40 gears right now (stock). What do you guys think I should put in?

Get the ratio in the 1.7 to 1.8 range