"Is it possible to update the software in a 2000? Reflash the memory to 7.8 standard? I know some ECU's can be reprogrammed, but have no idea if that is an option on the Boxster. If that is really the only difference, then shouldn't an ECU upgrade get me to 280hp or at least very close?"
I put in aftermarket intake and exhaust systems and had the ECU reprogrammed for a 2000 base boxster with higher flow intake and exhaust. The dyno showed that I only got a little over 25 hp from the mods, but it now also has a nice wide, flat torque curve.
Ed