My friends and I had a great trip this past week in the UP., We rode about 300 miles in two days...My 2005 Mach with 06 update, stock Clutching with extra pin weight, no decompression plugs, 144 studs, no other modifications. Sled never missed a heartbeat, absolutely NO issues with motor, 1800 miles on sled, 400 miles with 06 update...first 80 miles sled would start when cold then quit, then on cold startup after 80 miles would start and keep running...been good ever since...no problems top end, this sled flat out rips! Intresting fact...I had a chance to ride a 2006 600 SDI Renegade for about a hour...Awesome sled for the trails...gets 18 mpg brand new...My sled also got 18 mpg...some fillups I would get a tenth or two better, next fillup maybe the same...BRP I feel has done an excellent job with both sleds...In fact many times with our combined fuel consumption would be the same as 800 mxz...My Ski-Doo Dealer, Ray C's Ski-doo of Lapeer, MI. did the set-up and tuning on my sled...Thanks Ski-Doo and Ray C's for a great job and a great sled!!! Allen.