You must have a base set up for the 2 things I'm after for every car and track? Faster in straights what do I change? a straight is a straight whatever track.
Na, I don't...
Resistance slows you down. Things that affect resistance are:
Aero
Ride Height
Airflow
Toe
Caster
Differential... But most importantly, how you exit the corner leading onto the straight.
So in the most basic terms, I'd say reduce aero, toe and caster if you are only considering the straight on it's own.
When you talk about stability, I am not sure in what aspect you are looking to be more stable.
I'm guessing pitch or yaw, but it may equally be loose or pushing.
Generally it is up to the driver to manage this as the engineer has the long game in mind. You have to be careful, when you lack skill or experience, not to chase your bad habits.
For many people, they have become used to a certain style and adapt their setup for that. A car they never drove, will have diff doing this and suspension doing that before they've even done a lap.
Doing this only enforces the bad driver in you. You only become better at driving around your deficiencies instead of letting the car talk to you, telling you what it needs to be free.
I still dunno what car and track, but with the set you are using now...
Approach the turn you are having difficulty with. Brake hard and late but only for the first two downshifts. Now the car has scrubbed off the speed and is at a manageable level.
This is the point where all of your senses are heightened. Coming off the brake, the front of the car rises to its neutral position. This can be smooth or abrupt depending on suspension settings.
Your job as a driver is to negotiate the entry while keeping the car as flat as possible.
A bit more brake or a dab of throttle to settle the nose. As you enter the corner, you are constantly steering with the throttle. Do it well and you'll be on that edge of adhesion.
My guess is, this is the point where you are still braking. Instead of taking the corner like U it is more like V.
So pitch is the most important thing at this point but at mid corner, that turns into yaw.
As we exit, we now must juggle pitch and yaw, seesawing between the two to exit cleanly.
At each phase you as a driver need to identify is it pitch or yaw you are having trouble with.
Is it a setup or driving issue?
Pitch/Yaw is influenced by all the tools you have available in the car setup menu depending on which phase of the corner you are in.
So there is no simple answer for you I'm afraid Jim unless you just tighten things up a bit to see if those transition points don't settle down a bit for you.