I have the same noise at 5000-6000 rpm. I'm going to adjust my TPS this weekend and see if that fixes it. Check out this site, it contains the procedures for the adjustment of the TPS as well as instructions for making a homebuilt TPS tester. http://www.robertlyonsphotography.com/snowmobiling/tps.htm

I'm also looking for pipes for my 01 800 XC. From what SLP says you cannot use their pipes on Pump gas so I'm will probably go with PSI as well. I don't know if PSI has a clutch kit for the roller clutch though so I may get that from Goodwin. Does any one have any experience with this combo?

The Shade Tree mail order catalog has good prices and a discount with orders over 10 plugs.

I'm looking to pipe and clutch my '01 800 XC. Does anyone have any opinions on manufactures, good or bad. PSI makes pipes that claim 21 hp while others are around 17. Does this sound accurate? Thanks for the help.