I own a SMAN3 but also want to get an analog 4 port gauge set and think I found what I want at a great price. Problem is stuck because Im faced with 2 identical gauge set choices, one read in Kpa/PSI and the other set reads in BAR/PSI and Im drawing a blank. Can one of you set me strait on which is common for the AC residential use without having to crack the book as I as Im ready to buy online without my books handy?