Hi all, I just got my car with a new engine, the old one was really old moreover it seems to have a crack that makes it a waste of time saving it.
the new engine is a 91 model latest M30 and maybe the last. it's really clean and it runs silently. the thing that bothers me that it lacks power. the old engine had way better performance with average compression around 8lbs. I still didn't check the new engines compression and I have 7 other days to test it before the warranty is over.

any idea what's going on? would it be valve adj. or bad injectors? I need quick advice before I decide on keeping this engine.

P.S. this is a second hand engine from a trashed car imported from Japan.