I agree the tint makes a huge difference. My 82 911SC that I bought and drove in Texas for 3-4 years had marginal a/c even with the a/c components in perfect working order. Then I tinted it WOW! what a difference. My 92 500E had it done from the dealer or the original owner because it was sold in Arizona.
I bought the car used in Northern Va/ Washington DC area Any one that has been here in July and August can tell you the heat is bad the humidity is worse.
The 500E no problemo even in stop and go traffic.
The 85 300 SD is Pearl Black Metallic and I remember the a/c being marginal but I can not remember if that was before or after Dad had the a/c repaired.
I need to check his 3 inch thick file of maint. records ( bless his heart)
I do plan on having the windows tinted however in Va they are very restrictive on how dark. But again every bit helps.
Thanks
Alan

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )