First of all get an RB20 actuator - simple, cheap and stock looking. If that's not enough you could get a JayCar boost controller. It uses the stock boost solenoid (it would take a very switched on cop to notice the difference) and the only connections are to the ecu so you can put it in the glove box.
http://www.skylinesaustralia.com/forums/topic/61207-jaycar-boost-and-fuel-control/