This is for my 1996 9000 Aero, I know i want the auto meter Z-series gauges. They have 3 different boost gauges, which are
1) 30 in. hg. vacuum/20 psi
2) 30 in. hg. vacuum/30 psi
3) 0 to 35 psi
My question is what is the hg.? and what do i want it or not?
The second gauge i am looking to get is a Mechanical oil pressure gauge. They only have a 0-100 psi. Is that good enough because i have seen 0-150 and 1-200 psi ones also.
The last gauge i am looking at getting is the Oil Temp gauge. The two to choose from are
1) 100-250 degrees F.
2) 140-300 degrees F.
Which one is better, and these are both electrical gauges, would it be better to get mechanical ones? Thanks so much for you help. Also if anyoen has a better selection of gauges for the Aero instead of the three i have selected please let me know. I am new to saabs and am trying to learn.

hg = vacum
I still can't beleive that git Hugh Grant invented vacum http://www.smilies.nl/bounce/1blue1.gif

Is it good to have the vacum or do i not need it, what does it tell me, also to what psi should i get the different guages. Thanks again.

in. hg would be inches of mercury, or how tall of a column of mercury the vacuum can support. 30 inches is atmospheric pressure, so that would be total vacuum.

If the gauge is boost only, it will rest on it's zero pin until your turbo pressurized the intake manifold past atmospheric pressure. Not needed, your preference.

The stock boost limiter cuts in at 14.7 PSI, if I recall, so the 20 PSI gauge would work fine unless you wanted to bypass that and boost higher.

No idea on oil temp or pressure, sorry.

1 bar is about 14.5 psi, right?
Well, the oil pressure should not be more than 5-6 bar or so in your Saab at any time, so I reckon 100 psi should do fine. Anyway, some extra range won't hurt either.
I'm getting a 10 bar oil press. meter for my car, that's 145 psi, isn't it? That should be enough even with the engine mods that I'm planning on...