How to improve 986 driving feel?

[WhipE350]

I own both a 2007 Base with very low mileage (8k) and a 2000 'S' with 59k. In an effort to make the 2000 'S' feel more like new (and because I enjoy replacing stuff for the heck of it) I have replaced the shocks with new Bilsteins, front/rear drop links, front control arm link, front control arm, and rear control arm link. I have not replaced the rear control arm or track arm. I also now have brand new Michelin Pilot Super Sports on 18 inch rims.

Both cars feels so much alike but SO different. On tight twistys in the 20 to 50mph range both are awesome with the 2000 'S' being a little more predictable, in other words I'm more comfortable getting a little bit of slide and that I'm in charge of recovering from it (it doesn't have PSM).

What does bother me is the big difference in high speed highway driving over 80mph and driving on roads that are uneven i.e. lots of swells and dips. On the highway the 2007 will just cruise with no sense of how fast I'm really going, the 2000 seems twitchy and less steady, not a good feeling at speeds like that. On the uneven roads the 2000 seems to be pulled and steered by every swell, just feels busy.

Is this just the way it is or are their modifications I can make to the 2000 'S' (without making it back jarring) to give it more of that 2007 sure footedness? Or am I just a product of driving too many modern cars that hide everything that is really happening?

I probably won't be keeping the 2007 for more than a year and want to enjoy the 2000 to the fullest after the 2007 is gone.

Maybe these are dumb questions and nothing can be done. Really just trying to learn and i know there are guys that track all the time and understand this stuff much better than I do. Appreciate it.