The OEM wheels are generally lighter than their knock-off counterparts.
I also run 17" on street and track tires.
For my stickies I use Victoracers in 225 front and 255 rear on 7" and 8.5" OEM wheels.
The 225s help to dial out a bit of understeer.
You can see the fronts in the middle, sandwiched by the wider rears.
Happy Boxstering,
Pedro