One problem related to engine noise has been reported for the 2005 Porsche Boxster. The most recently reported issues are listed below.
Pulling away from a green light in traffic, the engine started to upshift into a higher gear much sooner than normal and the car felt down on power. The engine sounded as though it was running on fewer than normal cylinders. I stopped the vehicle immediately & had it towed to a Porsche specialist. They told me it was an ims (intermediate shaft) bearing failure and that is was a known problem with m96 and m97 Porsche engines. Mine being an m96 engine.