Lots of noise above half throttle, a lot more throaty down low, other than that you shed something like 7 or 8 lbs and it free's up some space under the hood. Performance gains are not proven, pretty hard to judge, you won't notice a loss or gain for the most part except for the wait reduction.
i know a few cases (i mean a few lol) where the sled could get the skis off the ground over the stock one. he switched the stock one and the rumble pack over a few times to make sure it wasnt in his head. in rare cases im sure it can. pretty much all cases it doesnt do much except make it sound better.
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