I'm pretty certain the used 2002 650 I bought has a stock tailpipe on it. All the videos I've watched of Savages sound like proper bikes, but mine sounds decidedly weaker. It sounds like a lawn mower, honestly - it sounds more mechanical than booming, if that makes sense.

I've noticed when it starts up on a relatively cool morning, steam and/or exhaust comes out of the spot where the pipe connects to the motor underneath the handlebars. Is this an exhaust leak, and would that account for the weak sound? Is it likely to be causing other problems? Can I fix it myself?

Be very careful with the header bolts . They are long and skinny and just begging to twist off. Use a 1/4" drive ratchet, thumb on the head of the ratchet, gently close your fingers to tighten. FEEL the bolt.
Start with the stock muffler.
It strangles the motor. Even before it rusts .

 I'd say its pretty normal for a 650 to sound like a sewing machine going down the road when you are on top of it.

 Sounds better from the side I say.