Hi Neil;
Call me stupid, but I flew the first 50 hours without knowing that I should have a restriction on that feed line.
I stumbled onto that info by accident. I can't remember exactly what size I used, but it was bigger than the recommended minimum which I found online somewhere. After I installed that, it improved my hot idle oil pressure.
All I did was plug the hose fitting with JBweld and then drill it out the next day.
I recently put a small bleed line on the end of my fuel rail where I needed a very small orifice so I used a Mikuni #40 pilot jet. I just tapped some threads inside the ¼" tube fitting that I used, then screwed the jet into it with some lock-tite.
If I was doing the oil line restriction today, I would do just that again, but using a Mikuni main jet of at least a #225.
I recently changed to a solid tube for a feed line since the engine and turbo are fixed with no relative motion between them, but before that I used a high temp hose, but the end at the turbo always showed signs of heat.
So I installed the orfice at the fitting coming out of the engine, reasoning that a leak in the hose or solid feed line wouldn't lose oil as fast as it would still be restricted by the orfice.
Thinking that in the unlikely event of an oil leak there hopefully it will show other noticable signs before a sudden loss of all oil pressure.
Todd