Ok from what i understand so far about the BMW engines is as follows>
M52 engine belonged to the early 3 series E39?
M52TU engine belonged to the 3 series E46 1999-20000?
M54 engine was introduced and belonged in the 2002 on-wards 3 series E46?
so whats the best engine, regards performance/reliability. and what changes were made i'm finding it hard to tell them apart?