I previously had the same symptoms as you have, and a new fan clutch totally fixed it. Last summer I ran my C for hours on the expressway with the A/C on full bore - on a humid 95 degree day - without nudging the temp needle above mid-range. You didn't mention your fan clutch being new, and since everything else in your system is like new, I am placing my bet that yours is slipping too much. Have you checked that possibility?
You can diagnose for this cause by seeing whether your fan turns, yet exhibits a fair bit of resistance, when the engine is turned off. It should not keep spinning by itself at all. If you do need a new clutch, the most effective one will be a thermal type, rather than a non-thermal - especially if you have a challenging situation.
Keith Boonstra
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