How to Install a Boost Gauge
This Volvo Forum topic covers installation of a boost gauge. Your model of Volvo might be different from the photos and description, but the concepts are there. Wiring, routing the vacuum line, mounting, it’s all here.
A boost gauge — I recommend the IPD “R” unit, the display is gorgeous — is mandatory for any serious further speed modifications.
I have an IPD A-pillar mount that is going in soon to house the gauge. Then the wiring and tube will be hidden and look professional, no silly double-sided tape to keep the gauge attached to the pilar.
You can go through the firewall like I did, or do it the smart way like D_V_ENT850R and tap into the line that goes to your boost gauge on the dash. You should be able to find it under there somewhere.
For wiring, I wired into the dimmer switch (pink wire on my ’97). Works perfectly, looks fantastic. For wiring done right, see this car wiring topic I started to know how to do it right next time.
Next up for me, manual boost controller