You should also change the size of the main jet in the carb, piaggio recommend a 58 but Taffspeed recommend a 60. I had derestricted this way before further tuning, washer, exhaust resonance tube and changed mainjet to a 60 and it went great. Read taffspeed's guide for the DNA, great info, I used it as a basis for all my tuning.
http://www.taffspeed.co.uk/page41.html
Steve
October 2006