Vintage Air System not too cool????!!!!

are you sure all the ducts are fitted on and sealed up ok?
so it was cooling ok at the shop with a 80 ambient and is no good at a 107 ambient?
You need to see if its sweating back when the ambient is high and fit your guages and see what the pressures are doing with the high ambient.The condensor fan switch will be fine so dont worry about that one as long as its still cycling ok.
You might find the condensor is under sized for the high ambient . So if its running over 350 psi on the discharge when the ambient is up and the fan is running then thats probably is whats going on .
So long as the suction pressure is around 20 psi , there wont be a blockage . If youre suction pressure is too high , its a possibility that the hot water valve isnt closing off all the way , to check that just crimp a hose off in the engine bay and see what it does . if its heating the evaporator , that will bring the suction pressure up.Most factory ac run at around 20 psi , i dont think it needs to be as low as 6 and on some machines that can be too low and you can run into oil pumping issues . Its not a great idea to run the fan all the time when the ac is on as you can have too low a head pressure which can cause other issues.If they charged about 800 grams into the system , it should be fine .Taking gas out will lower the suction pressure but depending on the size of your receiver drier , i imagine the gas charge isnt too far away . There could be an issue with how the condensor is mounted too , is it in front or behind the radiator ,and is there a gap around the engine fan / post a pic , that would help.
cheers Ben