It does'nt matter where you put the vaccum pipe as neither place is accurate as the boost is controlled electronically. To get an accurate reading you will need a digital boost gauge which wires in to the ecu.
To get the pipe through to the engine compartment, remove the scuttle panel, remove the wiper mechanism and there is a small plastic cover undo this and it you can put the hose through here, just feed it through and if you take the fuse box cover off you will see the hose poking through. voila. I did have a guide with pics on how to do it, but i cant find it sorry