Unfortunately, two strokes are always gonna be a lot louder than a comparable 4-stroke bike. Two-strokes are also under fire due to more exhaust pollution. For these reasons, new two stroke bikes (and boats) have already been banned in a lot of places..
If we all go riding around without a pipe (!!??) or silencer/muffler and upset the neighbors (most of whom vote), they might just pass another law that lets them confiscate all two strokes they catch on the street...
My guess is it'll happen worldwide anyway within 10 years or so.. but thats only if everyone is really careful about noise..
Anyway, a simple tapered/cone shaped pipe, with no baffles inside, will really help power. The cone (diffuser) will pull exhaust gases out of the cylinder. This will provide a cleaner fuel mixture to be trapped in the cylinder, and a lot more power will be produced. When followed by a good muffler, the bike will also be fairly quiet.