[Sophisticated Redneck]

Very nice ride and If you picked it up for 10k then you got a great deal on it, even with 130k HOWEVER you are in for a rough ride (pun intended) unless you get a warranty or work on it yourself.

It is a very complex machine (did you know your ride has 5 water pumps, 4 fuel pumps and 9 heat exchangers?) that orginally cost over 100k and it's parts are not cheap.... With that being said, here is what you need to do.

I am going to assume you have already checked all intake connections for leaks/holes/connection issues so:

First, test your wastegates. If they are not fully and tightly closed at -10psi (use vaccum hand pump to test), then they need to be rebuilt.

If the wastegates checkout then next up replace your two CCV tubes that run to the lower intakes manifolds. (One on each side). They are cheap corrugated plastic and notorious for cracking and only leaking under boost, not vacuum.

If still issues after this, replace your diverter valves, these get old and leak boost back into the intake, it would never show up on a vaccum test.

If still issues then replace the rest of the CCV lines, there are check valves in the upper lines that can go bad and leak boost into the crankcase.

If after all of this you still have issues then it's time to for the REALLY big stuff: pulling turbos and checking to see if they need to be rebuilt and checking your lower intake manifolds (requires engine removal).

Oh btw, unless they have been done in the past 50k, replace all of your coils and plugs now too. You will thank me later. Use Eldor coils and ngk 1 or 2 step colder plugs