No, you don't need a third can. You were undercharged before and probably slightly overcharged now. Your high side should be about 2.2 to 2.5 times ambient that would mean from about 170 to 190, but that would be with engine at a very fast idle and a fan in front of the car, so your pressures are not alarmingly too high.

Check your vacuum pods to make sure that you're not inadvertently getting outside air. Remove the glove box liner and check the lines on the manifold below the glove box. If there are any leaking, post which one or consult an FSM to see which is leaking. If it is the recirc pod, then there lies your problem.