[Wayne 962]

That's not exactly how it works. The 2004 Boxster engine is a 3-chain motor, which means it has the updated vane-cell adjusters for the camshafts. As such, in general, it's not a plug-in-play for the 2000 cars, because the Motronic version is 7.8, whereas the 2000 motors were 7.2.

I have an updated 996 factory-rebuilt 3.4 motor in my Boxster right now. The motor has some updates (intermediate shaft, seals, etc) that are compatible with the 1999 model year, but in general, it's mostly a 1999 engine, not a 2006 engine (when the engine was rebuilt). So, this motor is probably a 2000-style / core engine, with a bunch of good updates...

Hope this makes sense,

Wayne