Victoracer
V700
front (225/50/16), and rear (245/45/16)
or hoosiers in those sizes.
or keep the 17's and run V710's (the fastest tires available right now)
note that the 16's would not be legal for stock class (if it's an ap2)
most s2k solo2 guys also run a stiffer front sway bar. see the racing section at
www.s2ki.com for more details.