check this little read here
https://www.pelicanparts.com/techarticles/Boxster_Tech/11-ENGINE-911_Engine_Swap/11-ENGINE-911_Engine_Swap.htm
Quote "The Boxster 1997-99 chassis can accept any Carrera 996 3.4L engine, or can use any Boxster engine from 1997-2002. In 2003, Porsche switched to a vane-cell adjuster mechanism to control the variable camshaft timing, and this system requires the later DME running Motronic version 7.8. Unless you upgrade the car to use the later DME (very difficult), you cannot use any 2002 or later 996 Carrera engine or any 2003 or later Boxster engine. You can swap in any replacement 2.5L engine from 1997-99 without having to remap the DME."
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