an in-line restrictror is the way to go here.
Yes but a restrictor doesn't lower the pressure
That depends how you look at it. The turbo cartridge is sort of 'open' so the size of the restrictor determines the amount of oil the turbo gets. Too much oil to the turbo and he cardtridge will build up pressure and thats not good. Result then is indeed blown seals of the turbo and oil smoking.
The size of the restrictor (or size of the oil line) theoretically does somewhat determine the oil pressure loss of the engine, but I have never seen any difference in oil pressure running a turbo or without one.
So, in the very general I agree with 'baked beetle' although the manufactor of your turbo should give what size/amout of oil feed you need. Garrett for instance has good info on their's on their site
www.turbobygarrett.comI run my big Borg Warner with a 1,6mm restrictor. Not all turbo's like or want this however, so check before.