The TIM gauges aren't a bad gauge, my mate uses une in his mini turbo running 17psi.
Where is it plumbed into???
As for wiring it in, i've wired it into the fader, (makes it brighter / duller) plus it stays on all the time the ignition is on like the rev counter etc... 2 wires. there is a diagram in the
guide on leonturbo.co.uk or something. do a search on gauge backlight.