Had some Dunlop Direzza Red Stsrs or something like that and they were really sticky and had good street/rain tread. They were also the onliest tires I've ever had that actually blistered from getting too hot autocrossing. Would NOT want those for a hot climate.
The main reason I went to 18in wheels on my black 951 was better tire choice. Back when I had the white 951 and 928 GT there were still good tires choices for 16in wheels.
When I got the GTS it had 17s and there weren't any good tire choices anymore so went to 18s on it.
For the 944 the Carrers lightweights are a great 18in wheel...
The previous owner had the front suspension adjusted so low it rubbed cornering at speed. Had to raise it almost a half inch.
When autocrossing usually just got the stickiest street tires according to the tests on tire rack.
Got tired of changing to my slicks just because they were 2 seconds faster. And there were only one or two other cars running slicks anyway.