hey everyone...i just finished charging my a/c system today and i got it discharged and vaccumed...but added the charge myself...a book said i need 22 oz. of freon and 4 oz. of oil for my system...i did that and it only took it 25 psi...i used 2 12oz. cans...should i add more? i ask because i was told not to add more than two cans...let me know what you guys think..thanks