joekd, are you talking about putting a T connector on the area where the sending unit is for the low-pressure light? what type of line do you have to run to the gauge in that instance?
warlord, the whole point of gauges is to learn what normal indications are and then be able to spot problems based on that. for instance, if you see that your ammeter is showing a constant discharge, you probably need to take your alternator off and have it benched. or, if your oil pressure is low, it could be an indication of serious problems. just like the stock temp gauge...you know what's normal, if you see it suddenly going up then you will go and shut the car down and do some investigation, right? right.
and the point of a vacuum gauge is twofold. 1 you can tell if you have a vacuum system problem, aka LEAK. 2 you can measure fuel economy with it. numbers are different for different cars, but i recall someone here having done a vac gauge with a 2nd gen trep and said if you can keep it above 15psi then you are getting best economy.