just go ahead and dump some sand down the spark plug holes while your at it. Companies don't spend thousands of dollars tuning pipes for no reason... they aren't something to mess with unless you really know what your doing or you want to spend more money later in repair bills.
Like I said and like everyone else has agreed: don't drill holes in your pipes. Forget this idea completely. If you did it we all know in a few months or next year you'd make a post about how you messed up your sled and you're wondering what is wrong. Having your sled loud just for the sake of it being loud is pointless. Loud sleds can serve a purpose, but if you aren't a hotrodder it's stupid. One of the reasons people who hate snowmobiles hate them is the noise they make.
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