If you only have a vaccum/boost hose going directly to the gauge, you have a mechical gauge. If you have a seperate BAP unit that the hose goies to and electrical wires going from the BAP to the gauge, you have a electrical gauge.
You are tapped into a red vacuum line. Find the larger black hose, it is attached to the fuel rail pressure sensor on the front driver side of the Eaton. Tee your boost line into this line for a boost reading.
You should be able to hook up the hose to the correct line behind the glove box. there is a hose there going to the stock boost gauge. You can "T" into it there.