Portable Air/Fuel gauge?

First of all let me say thanks to BillGrissom, 67Dart273, 805moparkid, SirDan, and TrailBeast for all the info. As I stated before I am a real newbie with these air/fuel meters. If this subject has been covered elsewhere before I apologize. - But if there is ANY advice you can give me to direct me to finding/purchasing/understanding as much as possible about these, - I'd sure be grateful. I'd like to get a setup asap. Thanks.