993 Slicks -- 225/45/17 instead of 205/50/17?

[jmr3]

I think you should consider picking up a set of 18's.  With 8 or 8.5" fronts, 10 rears, a proper allignment, and maybe some mild fender rolling you can fit 245/35/18 up front and 285/30/18 in the rear of a 993. 

More meat generally equals more stick.