how do i derestrict an aprilia habana 125 custom?

You don't... It shouldn't be restricted as it is not a 50cc.
You can improve performance using performance modifications i.e. exhaust, rollers CDI etc but you are effectively only tinkering with a 5-10mph increase tops and changes to acceleration bandings. If you want faster then you'd better buy a bigger engined scoot... The Vespa GTS 250ie is a very well balanced scoot with a decent turn of speed, but you pay for that obviously..

Paul
December 2008