Mine rattles on start up and gets better as it warms up...also rattles at lower rpms when accelerating between 1000-2400 range. Was told it might be one of my cats because the sound seems to be coming from the exhaust. Getting a full diagnosis later this week.
Mine doesn't rattle when its cold or when its hot... It used to rattle for about 3-4 seconds on cold starts before I changed the cam chain guides, tensioners and variocam pads; But I haven't heard it since the rebuild
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Previously owned:
2000 Boxster S 3.2 Ocean Blue / 1974 911 Targa Silver