my box was definitely stock all the way, I just never tried hard jetting w/no other mods,,, but i'm 99% sure its been done.
I wish I could remember what jet was used, don't quote me on this but I'm thinking it was like either a 145 or 125, but I might suggest buying 3/4 different sizes (after you get confirmation as to correct range) and seeing if you notice the difference. I remember mine being on the larger side to error on the side of caution, but it could have been smaller)
(and remember that you should check that every few rides, you don't want it to clog, mine never did but i've been told they clog pretty easily)