ibasniper said:
Out of curiosity what gives the 3.0 si engine the extra grunt over the 3.0 M54
Nothing wrong with thinking of ways to improve on the original, but the fact is that supercharging (not turbo) seems to be the only practical way to extract significantly more power from any of the M54 engines. They all benefit from advanced variable valve and intake systems plus the fuelling, mapping and air intakes have all proven hard to improve on (claims are made, more noise is made, but bhp gains haven't really been substantiated with independent testing).
The N52 gained some extra ponies with a more sophisticated variable intake (not a Chinese blob-welded bean can :wink: ) better head design and reducing parasitic power loss, including by using an electric water pump. As far as I know none of the N52 kit will fit the M54. With these older engines the best route to more is power a proper service, decent fuel and maybe a vanos rebuild, but don't bother unless you have rough idle or soft pick-up.
Or buy an ///M