Chances are there is a limiter in the CDi box. Buy one of the auto advance dealies off of ebay. Look for one that has the same kind of connections as yours. It possible that you have a restrictiion in the exhaust header, but that's not really something you can remove. It's why i suggested a new pipe first and foremost.
Despite the common stories, I don't think there are often restriction "washers" in scooters that are easily removed.
oh, and I meant a technigas Next and a high flow filter. There was supposed to be a link in there but i must have made a typo.