If the orifice was plugged up, you wouldn't have any cooling at all. Are you measuring the amount of refrigerant you are charging the system with? Having the correct amount in the system is critical. Too much charge can cause low cooling as well.
Here is what we discovered in 2009 after deferring any repair until may 2009.
The pressure was indeed high enough to theoretically cool. The system had been recharged - supposedly - by Rosenthal Chevrolet in Arlington VA - they have idiots in the mechanics bays - the dealer mechanic did not evacuate the system so it had a significant amount of air in it. This was our theory anyway. Which proved to be true. Using a big shop air line and an air powered evac pump we pulled a vacuum to 28 lbs negative and held it 10 minutes. Then re-charged 2 pounds freon and it has been good to go ever since. Had i known when you and i originally corresponded that the dealer shop could be so lazy i would have gone back up there and stood on them until it was fixed at no further expense to me - as it is I had to put another 80$ into the evac and charge. So I am going to take a pass on your answer and offer the above story for your enlightenment.