Download the full N55 engine tech and service guide below. Warning - it's nearly 50mb in filesize.
The
N20 engine tech and service guide can be found at:
http://www.f30post.com/forums/showthread.php?t=856528
The
S63Tu (M5/M6) engine tech and service guide can be found at:
http://f10.m5post.com/forums/showthread.php?t=803494