now i know the basic stuff, and I know that these engines make a bit of noise, but i was wondering things more specifically, common problems, ect.

I know in a non overhead cam engine, you can take the oil fill cap off and get an idea of how the engine is doing, if you get alot of air coming out, you know it has bad rings and so on, but i'm not so sure this works with an overhead camed motor, but I would expect there to be alot more turbulence under the valve cover and it might be a different story.

I'm not even sure what the measurement is, but I assume things like boost and oil pressures arent being measured in psi, and I dont know the conversion, I have seen 1 metric boost gauge that went up to 1.5 of something, and like, -60 of something. It hit about -50, and .8 and i was wondering what that should look like, as i know both numbers are very important. Vacuum can tell you about leaks and whatnot, and boost can tell you similar things. I know these cars (the one im thinking about right now is an 06) run about 21 psi, and falloff to about 18ish at wot. was just wondering what that equated to.

if the tranny or transfer case is going bad, what kinda whining noise is that gonna be like, subtle, and something i really have to look for, or super noticeable.