I agree with what has been said. My guess would be you still have a bolt that is not loose/out. In my 2004 there is/was one bolt that went from front to back. If you are looking from the back of the vehicle forward, it was at about 5 o'clock. This is a shorter bolt and was in the opposite direction from the rest. Perhaps you could check this? What year is your Boxster?
Below pic may help. The bolt/position I am talking about is seen clearly in this one...
Hope it helps... My car is still up on jack stands and I can send you more pics if needed...
