I'm planning on installing a vacuum gauge in mine. Since my 2-speed switch isn't set up for an adapter,I'll plumb it into the line at the firewall. A friend of mine had one,and he could monitor for performance,economy,and,best of all,will tell you when your engine is running "below-par". That usually happens,when it's time for a tune-up,anyway!L.O.L. Just goes with what Mike B. says. It's like an on-board,old-fashioned diagnostic tool. Works best when combined with tach.
