So when my ac is on it mostly comes out the dash vents but some comes out of the defrost vents. Like 70-30 I guess. If I am not mistaken it is all controlled by vacuum. Any suggestions?
You are correct, i would check for vacuum leaks.
The nice thing is, the climate control and hubs are ALL that is vacuum controlled. My F150 had a vacuum leak that made it run like junk, took me months to find.
I hear the hub lines are a common spot for the leaks.
Also, the little valve on the passenger side near the firewall behind the oil fill cap. It's black and a little bigger than a golf ball. The hose fell off of it on my truck and caused the same symptom. Easy fix. Just find the hose and reconnect it to the valve.
Search for this thread, it is helpful too. 'AC blows out Defrost'