just bought my evo and how do I tell what turbo it has and what psi it's set at?

 

Factory boost gauge

 

when I'm driving it'll just go up? or at higher rpms?

 

You should be building boost almost all the time. If your factory gauge is working you can watching it go up. If you get on it you will see the boost spike and that is what psi your running.
As for what turbo you have there should be engravings on a flat spot on the compressor side of the turbo. You can get your information there.

 

If you have the stock 9 turbo it's 10.5 stock psi is 19 at peak boost, as stated above the flat spot on the compressor side says it all. And of course check your boost gauge as well when you WOT and it'll show with the needle.