I am looking into Speedhut gauges. Revolution Gauges to be specific. Now my question is this....I would like to buy the things that I have been looking into, they are.....

GR-AF-01
Revolution 2-1/16 Air / Fuel ratio custom gauge (w/ Dual Peak)

GR-VOLT-01
Revolution 2-1/16 Volt

GR-OIL-01
Revolution 2-1/16 Oil 0-100 psi (w/ Dual Peak)

GR-BOOST-04
Revolution 2-1/16 in. Boost/vac -30inhg - 30psi (w/ Dual Peak)

G-SHIFT-04
Shift Light/Warning Red LED color, Black Tube

Now about the volt gauge, I know what they are and they're specifically for my stereo system when to be installed. As well as shift light. The oil psi, boost/vac 30inhg ,is that really necessary? I am planning to use the boost gauge but I don't know if the boost/vac is really necessary and what are the difference if I get them separately instead? I just cannot stand to be not knowing what's going on with my engine, turbo and whatnot. I just want to be informed as I am sure we all do with our engine. I want to use 3 gauges to be exact, and debating on the middle pod that goes on dash or the a-pillar setup. Or use 5 gauges, by using 3 gauge pod for the middle dash and use 2 gauge a-pillar pod.