Re: 2004 E60 530i
its different engine.. 2004 and below all are using the M54 Engine. All cars afer 2004, they're using the new Valvetronic N52 Engine...
Depends on what is your needs, the M54 got more mod potential at the moment...
The N52, you gotta wait at least another year or so, before any serious mods will come out... but the fuel consumption for the new engine is supposed to be better than the M54.