Running warm when driving

i would say ur thermostat is two low ur car should run at 190 give or take 10 degrees when u get up to higher speeds in return ur engine is running hotter there for if u have a 160 it will stick open and closed at the time even though u have a high flow radiator it can kill ur temp by not giving time to cool cause its taking in coolant and then right back out also ur cap psi rating my be to high just some thoughts

More heat rejection is needed at speed than while idling.

Be sure the radiator is sealed around its perimeter. This includes between the condenser and radiator.
Be sure the condenser and radiator are free of debris (leaves, garbage bags, etc sometimes stick to the front of the coils).

It is possible that the t-stat is defective. Higher RPM driving can allow the pellet to be damaged in unbalanced t-stats (in balanced stats, the pellet is shrouded).

The cooling system is a closed system, and one with inherant restrictions to flow. I don't know that a swap to a 180 t-stat would change anything, other than phase-shift your ultimate operating temp. In the summer here (So. Arizona), stats are often running at WOT (so to speak. The car operates well above the stat rating, so the stat never closes once up to temp). The closed nature of the system and restrictions allow the system to function properly.

I would seal around the coils and swap t-stats (just to try to be sure your have a fully functional one).

Good luck

If you suspect a leak in the system, put a cooling system pressure tester on and see if it holds steady for an extended period.

Does the amount of load while at speed make any difference? If not, and a light load causes it to run as hot as a heavy load, the issue is probably something ancillary.