mudski,

Those figures that I quoted are generally conservative safe levels for setting up. You can go a bit higher if you like, but then you may have limp mode issues and need to go back a bit.

I normally start by setting up the needle valve first and do this by closing it all the way (clockwise) and start the engine. Watch the turbo actuator as you begin to open the needle valve and when you see the actuator begin to drop away from it's stop screw, leave it there for the time being. Then go for a drive and see how high your boost goes. Ideally it should spike to around 16 or 17 and settle at 15 with a bit of throttle and load. Drive it normally as you would taking off at the traffic lights. Then just stop and make adjustments until you get it right. Even at full throttle, the Dawes should hold your boost at it's set point until you go over about 3500rpm, where the turbo will overcome the Dawes and your boost should continue to rise up to 18psi at 4000rpm. If you can't get enough boost with the Dawes adjusted all the way in, then you may need to stretch the internal spring slightly until you can. Quite often we need to stretch them about 5mm to get the 15psi setting.

After that, you may be able to increase or decrease boost slightly on the run with the needle valve. I use to close it sometimes going up hills to help EGT's and could get 3psi adjustment with about one turn.

If your car is a GUII, you'll have the vacuum canister. Nissan wisely omitted them on the GUIII and later. I've found quite a few that caused problems when they cracked from heat. If you have any low vacuum issues, just remove the canister and bypass it. You won't notice any difference.