I added a boost gauge vacuum line and a vented opti vacuum line along with the vacuum line to the msd 6btm. They we're all on the drivers side tapped into the same vacuum fitting for the fuel pressure regulator or the egr (Can't remember right now). Is there a point where having 4 things using the same fitting to much?

 

For the boost/vacuum gauge, use a vacuum connection that does not have any "flow". That means do not use the same vacuum port as the Opti or the PCV valve. The EGR port would be OK, if that's not where you tapped in the vented Opti. The vacuum source for the fuel pressure regulator is on the passenger side, along with the connection for the HVAC control vacuum. I would attach the vacuum/boost gauge to one of those, using a "tee".

The Opti is fine connected to the same port as the EGR vacuum line. That's where I tied mine in.