I will probably be buying a friends 2000 540i sport within the week. My question is what are some great mods for more power still keeping the engine N/A. I'm not looking for gobs of power, I just want to take it up a level. I'm fairly new to the 5 series, but not to BMW. I've been searching quite a bit. The car has the Eisenmann rear section exhaust, UUC short shifter, and some sort of chip. I would like some suggestions on further mods I could do without a F/I application. Your help would be much appreciated. Thank You.

Other than headers, which are of minimal value given the cost, there is not a lot to do, really, unless you want to start spending big bucks. Mods are something like this:
1. CAI (Home depot CAI is just as good as Dinan, just 1/8th the cost)
2. Shark (OBD-II equivalent of chipping)
3. Cat-back Exhaust
5. Add LSD (3.64 is considered a tad too much. A lot of people like 3.45)
4. Lightened flywheel (increases drivetrain efficiency by reducing rotating mass, supposedly, which makes sense from a ME perspective. Increases gearbox noise for some people, although I never had that problem)
5. Full exhaust (headers, racing cats, whole deal. $$)
6. M5 cams (supposedly helps up top. $$$)
7. Standalone Management (Tec3, that sort of thing. $$$$)

All told, though, those mods will only gain you perhaps 40 hp/ 40 ft-lbs. Although I do not know about the results of the cam switch.