I'm having a little difficulty in understanding your problem.  But I think you are saying that sometimes your bike runs fine and at other times it has so little torque that you can barely get up the hills but it still revs up to high RPMs when in low gear.

This sounds like a fueling problem.  At times the engine is getting enough fuel and at other times there is not enough fuel going into the carburetor.  The vacuum operated petcock is known to fail and work intermittently.  The solution is to replace it with a new one form Suzuki or replace it with a manually operated petcock made for the Raptor.  Or it could be as simple as a leak in the vacuum hose going from the carburetor to the petcock.

This problem is discussed at length in the tech section including instructions on how to test your OEM petcock and how to replace it.  Most people recommend replacing it with the Raptor petcock.

Take this link and go to about the third section down and near the bottom of that section is a heading that reads Petcock, you'll find several helpful links there.  
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1181745927