I have a 56 plate dtx 125, an I raced my mate on his fully deristricted aprillia mx 125 an I'm keeping with him all the time, topped out at 97 mph!!
All it has is a full arrow exhaust system
Speedo grey wire mod on the bk of the clocks (allows it to rev higher)
Sprockets and chain
And main jet was apparently changed to a jet higher before I had the bike
An the plastic bottle on the left-hand side of the air filter box I leave to hang so it breaths better.