The carb is a CV carb that I haven't seen on any other model, though I've never seen a Dommie in person. I would imagine the same carb is used.
Unplugging it and getting more power means it'll get louder. You'll notice it gets louder if you even put a foam air filter in it.
To get more power you can remove the snorkel from the airbox and you can grind off the welds on the muffler baffle and replace it with a baffle from Thumper Racing, at which point you must richen the jetting (they're pretty lean stock but it won't run with stock jetting after these mods) The bike will get significantly louder but it's not obnoxious. More power = more airflow = more noise, unfortunately.
There aren't any mufflers on the market that I've seen that aren't significantly louder than stock, so I think you'll have to decide what's more important to you there.
As for a kickstarter, I've been told an XR600R kickstart setup will fit on the bike but I can't verfiy that.
Talk to Baja Designs about the battery - I believe they've done just what you're looking to do. Panniers do sit wide with the battery in its stock location.
Cheers,
Wright
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Wright Bagwell
http://www.geocities.com/wwbagwell/