I have an mbrp. It robbed about 4 mph on the topend. About the same down low. It is and was annoyingly loud. Like something you'd here at the I-500. Any non-snowmobiling person hated it. I took it off and put the stock one back on. And thats whats staying on it. Bob had a bender on his 01, and that was on the loud side also. It lost about the same amount of power as the mbrp. When he would start his up next to me, I had to look at my tach to make sure it was still running.
My advice is to save your money for a different rear skid, a good track, and studds.