[thstone]

Its all about tolerances.

Replacing the clutch and flywheel with OEM parts is generally an accepted practice - that is why the dual mass flywheel is there, to mitigate (to an acceptable tolerance according to Porsche) the imbalance imparted by the original parts and any change in balance as they wear and any changes from the new replacement parts.

If you have the time and the means, you can statically weigh/balance the new clutch parts. If you have more time and money you can dynamically balance the new clutch parts. Its the same idea as balancing your wheels/tires.

Its the same with engine rebuilding. You can do a DIY job and not balance anything. Or you can have a machine shop weight match some components. Or you can weigh and balance everything.