Where is the best place to tap into for the most accurate reading with an aftermarket boost gauge, is there any fittings I need, where do I get them. Thanks-

If you're talking about an 87 GN, then I would hook it up to one of the vaccum lines right behind the alt. You can get a tee if needed and a rubber fitting for the small boost guage line at any AutoZone/Advance store. Just make sure it's a real tight fit, otherwise it will blow off.HTH