I've just finished running in a new OS XZ-12 SPEC 3 engine. I couldn't believe how quickly it ran in and became stable compared to my usual novarossi's. I only got it as a backup backup engine as the price was right. It is incredibly powerful and linear in its power delivery. Sounds good too for the price I think it is a brilliant engine. I still prefer my nova virtus though which is more powerful overall once they finally run in!