I can understand the reasoning behind 5000Km of mineral oil....but not really on a Subaru engine, on something agricultural like a cast iron V8 in may be necessary because the way they are built(ie agricultural slop) but a subaru is really quiet a well engineered thing.
The whole reason for "run-in" on any engine is to "wear-in" the parts that were not machined perfectly, the rings are bedded in the first 30Km, so some good wot runs must be done in the first 30Km to push them into the bore filing/hone, after that the filing is worn away and rings will not get proper shape.
The rest of the run-in period, usually 1000Km is to wear the bearings into shape....again better the clearances and machining the less wear-in required.
On a built motor i usually go 30-50Km from first start-up to warm(no idling or screwing around...first start up you drive it) onto freeway wot 80-110 in 4th a few times, wot 80-110 in 5th a few times...repeat for 30-50Km, usually on wastegate pressure ~18psi, 4500rpm limit, ignore the stupid looks you'll get from other drivers lol.
Then drive it as normal for ~7-800Km 5K rev limit, in the last ~150Km of that start revving it out to 6-7K.
Change oil to synthetic and tune for power or ~1.8bar, i would leave tuning for anything past 600hp until ~2000Km.
I have tuned an engine past 650hp after a 600Km run in period that was done in 2 days, all good.
Tl;DR Subaru's are modern and well machined, don't need fa run in just drive it....life begins at 30psi, 18psi should be wastegate pressure
