Boost guage install!
http://www.xse.com/leres/ss/gaugepod.html
I love the setup. I also did the fan indicating lights, except I did yellow for low speed and red for high speed. To answer your other question, my personal opinion (I know nothing about boost...) is water temp (if your year is 1999 or later) and oil temperature. I also did the alternative action switch, and I think it's great.
this was makeshift before I switched the clear tube with vac line...

