Hi anolog, mate best way in my opinion is to check out some setup guides, there's a good one for nKP
here just follow the link, its a very good guide IMO and the fact its for netKarPro is even better, otherwise Google race car chassis tuning guide or something similar and you should get plenty of hits
I would start with spring rates then tyre pressure, if no joy there look at dampers or downforce, sometimes its a little of each thats why I suggested the setup guide, everyone's driving style is different and so are car setups.
Ive downloaded setups that are really quick, but they don't suit my driving style so I'm actually slower with them than my own, it only really suits the guy that made it or guys with similar styles.
I think car setups are kinda unique to the driver, an extension of the driver you might say, and a good setup can bring car and driver together as one, making for smoother driving and faster lap times, but its rare that "one drivers setup is another drivers lap record".
You right about tire temps too 80 is optimum for nKP.
Hope the guide helps, let us know how you get on mate
Cheers