[Anker]

I would start with the suspension and retorque all the nuts and bolts. I would also check all suspension bushings and ball joints for wear. Then the engine plus transmission mounts. Also all nuts and bolts on the exhaust.

If that doesn't fix the problem I would go to a body shop and have them do a thorough check. They are able to measure the car to check whether there is any deformation of the body.

If the car ever has been in an accident I would have the vicinity of the accident damage checked first.

The Boxster body is strong and has very little flex. An undamaged body should not creak under the circumstances you describe.

Hope this helps!