Actually it depends on what you want to read.
If all you are concerned about is the boost level seen by the engine heads then plumb the line into the intake manifold after the throttle.
If you want to also see if spikes exist during closed throttle events then plumb the line before the throttle.
If you are interested in the shortest path to run a line then plumb it into the brake vac system.
The stock location for a 930 is plumbed into the BOV housing - before the throttle. If you use a tattle tale gauge plumbed into the stock location it will record boost spikes.
As for line material, if you desire the least expensive material use plastic tubing. If you desire the most robust use S/S braided line.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8