The car was modified before I purchased it, but then they attempted to throw it back to stock.

My vac at idle jumps around between 17-18ish, and even under boost it looks like the boost gauge needle can't settle on 20, it jumps back and forth 19-20 very quickly. The idle is a little sloppy as well. And it idles around 850-900prm.

Am I dealing with a valve/engine issue?

 

Easiest way to confirm would be to pull the valvecover. It's only a 10 minute job and a great way to confirm it 100%.

 

+1 for that...valve cover takes about10-20mins...took mine off just last wkend...if you are cammed the company will have the name on the cam most likely...

 

I would highly doubt its cammed. Thats very close to stock vaccum for a 4G63. My car went from 17/18 to 15 by just throwing in an exhaust cam.

 

Ok, so should I be concerned that the vac doesn't hold steady at idle?

 

the problem is, you can only tell IF its cammed, not the degree its cammed. i would try to contact the previous owner or something to try to find out.

 

sounds like your best bet is to contact the previous owner