All sorted. I found a plug behind the intake manifold which i guess is an unused vacuum port. Turns out the Speco gauge kit I bought has an adapter that fits! So no tapping into anything, the boost gauge has a dedicated vac port. I ended up mounting the gauge to the RH air vent. I removed the complete vent and cut out the inner fins. The 52mm gauge popped straight in nice and firm. Now the gauge swivels just like the air vent did. Really good kit considering the price.