Definitely keep your warranty because that sounds like no vales or lifters I've ever heard. However I would try the mystery oil it does work wonders sometimes. Now those 40 hrs labor to pull that motor has got to be to open it up to check for ware on other parts. Your car does sound like the one that was posted earlier. If you drive it till it brakes your warranty will get you another motor, if Porsche tears it down they"ll say the obvious shaft and prolly report on other things that should be replaced while it's torn down. good luck and maybe I'm wrong and it's just something else.