You pull back the carpet a little and you'll see a wire harness and I guess it depends on where your ngauge is because I have mine mounted in my dash so I routed the wire up through a hole into the vent...in your case you might have to just use one of the drivers side and mount the box under the...
I used the passenger 1/8 npt and mounted my boost + right behind my pass side foot panel fuse box...just ran a vacuum line through the firewall through a rubber grommet into the fender and up
Should pick up a good bit if dynoed in 5th.. I drive with knock limiting turned off just because I have 93 in my area but I also watch for knock on my gauge just to be safe