vacum problems

[waltz]

i just bought a 1990 eagle talon tsi, and the guy who had it before me supposeably put in a 16g turbo. right now my vacum pressure at idle reads 5. im new at turbos and everything but im pretty sure the reg vacum at idle is around 20. would a bad vacum tube cause this or is it a more complex problem?

 

[knochgoon24]

Either a cracked/ split / nicked vacuum line or leaking TB seals.
The larger cams also decrease your vacuum at idle. 272s usually see about 13-15inHg if I'm not mistaken.