[SD987]

There's some significant chassis/suspension changes between the two models but I'm thinking the difference you noticed was the variable steering ratio on the 9X7s which use hydraulically-assisted rack-and-pinion steering.

The ratio around the center position, i.e. for small movements of the steering wheel, is similar to that of the 986. As a result, the vehicle remains very smooth at high speeds. But the steering ratio becomes increasingly more direct with steering wheel movements of more than 30° to 240° (approx. 1/8 to 3/4 steering wheel revolution). This is achieved through a gear rack with variable tooth pitch.

The steering wheel revolutions from stop to stop were also reduced from 2.98 on the 986 to 2.62 on the 987 which greatly improves agility.

As far as the 19s verse the 17s, I had 17s on my 987 base and 19s on my 987S (which also has PASM) and the handling feels pretty much the same. If anything, I'd actually say the 987 base feels more tossable than the S although I think there are other factors that give this impression in addition to the tires. However, I think the 987S would run a faster slalom time, although it might not feel like you were going as fast. I don't feel the 19s with Sport mode is too harsh, although I'm one of those who think the 987 is best suited for 18s, which would lead me to believe that 19s aren't the best fit for the 986 (although I obviously don't have an owners perspective there).