Falken RT-615Ks are a good tire for a time attack style race were you do just a few laps. they heat up quick and are sticky and meet the 140 requirement. For 25-30 HPDEs they get greasy but still not bad.

They have these for the 18in wheels in 235/295. Not affiliated with this site, just throwing out another option. I actually use TireRack more.

http://www.discounttiredirect.com/di...%2FPerformance

 

Another choice are the Nitto NT05 available in 235/40/18 or 245/40/18 and 295/35/18. Review seems good and price is good with 200 rating. Any actual feedback from 997 drivers?

 

Falken 615k: The rear 295/40/18 is too tall unless you use the 315/30/18 but you need at least 11" wheels.