Toyota Repair: 2005 Sequoia AC problems, service bulletins, temperature readings

Question
I've got a 2005 Sequoia Limited 4wd w/50K miles; Lately, it's been extremely hot outside, and the AC is not blowing cold.  I purchased a small guage and placed it inside the interior vent to monitor the temperature of the AC; In the mornings, it will blow around 50 degrees, however in the afternoons, it stuggles to blow 60, and I mean it struggles.  I took it to the dealership today, they checked everything over, no leaks, vac'd and recharged the system and they said it was much better.  Well-not so fast.  It's not any better than it was before.  I asked the service mgr if there were any service bulletins on the Sequoia's AC, he said there were not and consulted his 'master tech' who confirmed our Sequoia had no problems.  This doesn't seem right, as the AC just isn't blowing cold, and it's certainly not cooling the cabin down.  I've had 9 previous Toyotas and never experienced this with one just a few years old.  Your thoughts?  Thanks!

Answer
I did confirm that there are no sevice bulletins on this year model but those vent temperature readings are not cold enough, they should be between 39-48 degrees F. There is a problem with this a/c system, the dealer should make sure they have a qualified a/c technician check this system, if they can't then you should either contact another dealer in the area or try an independent a/c repair shop.