Update:
I spent 7 hours yesterday (yay for Monday off work) installing my new boost gauge. I mounted the MAP sensor on the little bracket that holds the diagnostics port, near the factory 'turbo pressure sensor'. The MAP sensor is 'teed' off the stock vac hose that goes into the 'turbo pressure sensor'. I ran the 3 wires down the passenger side of the car, through the big grommet there then behind the carpet and down the centre along near the gearshift cables. I just soldered/spliced into the radio harness for switched +12V and used the ground the same as for the radio. Dimmer wiring was a piece of cake - just cut the green looking wire off the cigarette lighter bulb socket and used that. The gauge was mounted just below in headunit in the empty DIN slot and I just drilled a 10mm hole to feed the wires in the back.
The unit was a bit technical to configure as it reads absolute atmosphere pressure default so I had to set it up to -14.7 psi so it'll read 0.0 psi when engine is off. Also had to set the resolution too, which I got wrong the first time and went for a drive and was showing part throttle as 26+ psi???! ended just having to configure it again and it was all good. Very happy with the response of the MAP sensor install, seems like there is no delay at all with the vacuum readings or boost. Just a quick squirt in 2nd saw about 11-12 psi last night, just factory boost TVSV. It also has a great little function to save the MAX (peak) boost reading and you can recall this at any time with the button and also reset. Later on I will wire in a piezoelectric beeper to the alarm output for 'overboost' warning, once I eliminate factory fuel cut.
Pics to come.