Thinking of getting some gauges.
 

I drive a 93 Voyager auto 2.4l 4cyl and all the instrumentation it has is a speedo, fuel gauge and water temp. I was thinking of adding a Tach, vacuum and volt or amp gauge. I'm not sure if they will help me in my quest for better mpg but they would give me a better idea of how the car is running.

I was planning on mounting these in the spot where the radio was(someone stole it). I figure I have room for 3 or maybe 4 gauges. Anyone have suggestions on what gauges might benefit me the most?