When I crank it up there is a very irritating squeal coming from the vacuum pump "area." I recently changed the tensioner pulley so that is not it for sure. It goes on for a bit then quiets down. Sometimes it never quiets down. I am worried it is about to go and grenade my belt.

Should I replace the pump, or get the PCM/mechanical wastegate upgrade?

 

First Id take your belt of before you start it one day and spin some components around to see what seems to be hard to turn or have play in it, do that so you have a better idea of the issue rather than wasteing money.

 

X 2 what ranchhand says I have seen bad belt tensioners tear up a few alternators as well as a couple of P.S. pumps take that belt off and check out whats going on before spending money.