It is a mechanical boost gauge. For the pressure reading I T'd into the vacuum line on the passenger side rear of the intake manifold. For the power/ground i spliced into the trailer brake wiring harness.
The install was very and took maybe a total of 2 hours start to finish. The only part of the dash that has to come off is the piece that the vent is on and it just pops out, very easy. Yes you have to go through the firewall to get to the vacume line, i cut a small hole in the main wiring harness boot and pushed it through there, the boot is a soft rubber/foam that seals nicely around the vacume line once it is pushed through. All in all it is a very easy install especially if your somewhat mechanically inclined.How difficult was the install? Did you have to tear the dash apart at all? To get to the vacuum line did you have to go through the firewall? I really like the look of this gauge just want to know what im getting into before I go and purchase one.