I have been persevering with Subaru engines in a 9A since starting with an NSI package about nine years ago. The latest iteration was an MPS 2.6 "stroker" modified EJ253 with a compression ratio of 10.4:1. It had about 5% more capacity than a stock EJ25 and was the subject of some discussion in the forums a couple of years ago when its performance in the now defunct MPS's Glastar was queried.
I finally got around to flying behind this engine which for me was Subaru #6 and was concentrating on fuel mapping to give ROP at 5,000 RPM or higher and LOP at lesser revolutions. I am still using the NSI 2.12:1 gearbox and prop (which has 22⁰ of reverse pitch available).
There has been significant concern about this engine since the first one to fly failed in the Glastar due to piston damage causing the oil to be blown out through the rocker cover breathers.
At about 7 hours total run time I experienced a similar failure in flight and the event was captured on a panel/cockpit camera. Footage is on Vimeo along with some other footage which gives a better look at the farm strip I fly off. Links are https://vimeo.com/82777093
I am ashamed to say that I did not pick up the loss of oil pressure for a couple of minutes (the gauge is the small middle one to the left of the tacho) so expect things to look pretty bad on disassembly.
Other aspects which I should probably mention is that power is controlled by adjusting prop pitch with the L-R function of the coolie hat switch on the stick. You can see the very significant power drop when the engine goes >120⁰ LOP (peak is about 1450⁰) at 5,000 RPM and vice versa.
The landing was not well judged with 90 KIAS over the fence to a downhill strip but winding the prop back into beta always works well because the sprague clutch in the gearbox allows the prop to windmill without impedance and then this energy is used as an air brake as the pitch goes negative.
Earlier in the video you can see the aircraft's maximum performance which is about 163 KIAS at 2,000' although the density altitude on the day was closer to 3,500' which would suggest a KTAS of about 172.
I have thought about starting again with a proven engine/prop configuration but will probably go again with Subaru as I am still enjoying the challenge.
Regards from Australia.