I have a different car for the track, but it's fun to take the 991 TTS out a few times to play with it.

I didn't buy a GT3 because they are not what I want for street driving.

 

Same. Besides, the GT3 is only a "track" car in that it has less things to brake and comes with a different setup than the TTS. Give the TTS a track alignment (GT3 specs are a good start) and some sticky tires, it will out-lap a GT3.

But you probably won't want to do a 4+ hour endurance event in one, and you'll have to race in an unlimited class if you wanted to race it.