i would look on ebay for a new pipe. get an expansion chamber such as the tecno boss. ive never dealt with your bike so i don't know whats out there but if wost comes to wost then you can get a 2 piece biturbo and weld up your muffler header to the biturbo pipe.
you could also see if you bike has any restrictions such as airfilter or intake restrictions.
and last you could re gear.
for more acceleration you want a bigger rear sprocket or smaller front.
you could also go with a new carb. dellorto's the way to go if you want that.
def look at the wiki. it's alot of help.
just spend some time online researching what your going to do before doing it.
okay im done. sorry for the long post but thats whats you gotta do. :P