Whitbread - This is now an ancient thread, but a good read none the less... I had a local turbo shop do a genuine IHI RHB31 install on a 2015 AC 700 Diesel similar to the one in this now infamous modding post. Test drove it today and we noticed that some oil drops had sprayed out of the dipstick tube while driving it about 1/2 a mile (the dipstick wasn't fitting in there tightly and I can't remember if there were ever o-rings on it or not to hold it in tighter). In any event, the shop recommended either just putting o-rings on the dipstick or adding crankcase ventilation. My thinking on this is to go ahead with the o-rings, but to also have a breather added that just vents to the environment rather than trying to recirculate. Perhaps just drilling a hole in the valve cover and adding a short tube with a small breather filter at the end?
The turbo oil supply is through a 1.5mm restrictor (I assume this is needed given it's a journal bearing turbo) and drains back down to the pan similar to your 2007. Otherwise, there's nothing special - turbo installed in exhaust stream and compressor supplied by stock filter in normal location and routed to engine intake with aluminum tubing.
I didn't notice much of anything in the way of increased performance, but I haven't adjusted the fuel screw yet either, so I assume I already have enough air for the limited amount of fuel being provided, even at high altitude (5000'). I didn't notice a whistle, but I also have the stock exhaust on so that could be keeping it quiet. I guess the crankcase being pressurized is good confirmation that the intake is pressurized and the system is generally working, just needs more fuel to wake it up and take advantage of the increased air.
I'd really appreciate your thoughts.