Update: the car has run fine for 500 miles now. There is plenty of power, it passed smog inspection easily, and it maintains good oil pressure...most of the time. I have seen some lingering low oil pressure issues: at hot idle it holds just under 1bar, but the pressure goes up at least 1bar per 1000 rpms (e.g. 2bar at 2000, 3bar at 3000...and so on). I have experienced the low oil pressure warning exactly once after a long highway run at high rpms ("Italian tuneup"), and it's on a mix of 5w30 and 15w40 diesel oil. In the summertime I may move to 5w40 diesel oil and if the low pressure warnings continue experiment with an Xw50 oil or some thickener product (really hoping I won't have to do that though).
I actually ended up selling my really nice 2002 sedan and am using this for a daily driver now. If it lasts 10k miles or more I'll be satisfied, but would be nice to get at least 25k out of it.