If u want more power go after the clutching. It doesnt get u more power but it puts what power you do have on the snow better. And withe the pipe mod it has a different power curve now. U need 2 clutch the engine correctly 4 the power curve before anything else. My f5 beets my dads 600sdi 0-40mph cus' of my clutch kit.
I put the ovs clutch kit in my M7 with the speedwerx silver secondary spring and the blue silver slp in the primary and love my clutching the way it is. The thing runs good, I should probably just leave it alone.
Twins are finicky but do make good power. I have never ran them personally because they are finicky but I think most guys are getting around 160hp out of them. Hope that helps answer your questions some. Personally I would look at the BMP porting before the twins as it makes the same if not a shade more power and is alot more reliable from what i've heard and experienced. Much easier to tune and clutch for also.
i am looking into the same thing for my 06 m7 thin air is testing a couple right now and are going to show me the dyno sheets and tell me how they ride on the mountain so i am waiting for them let you know when i find out