http://www.nissansilvia.co.uk/vbb/sh...light=manifold
above is the original thread, although some of the pics have been deleted, but work your way through.
Ext wastegate is a pain in terms of fabrication but the boost doesnt spike and is super stable. with the extra gasses exiting to the atmosphere (rather than rejoining the main exh) theres less back pressure restriction meaning a 2.5" system is fine for near 300hp. with internal wastegate it would probably need a 3" system which would be tight to fit in my car.