If I recall correctly, the Porsche Program Manager of the 500 E stated in one of of the two Porsche 30 year 500 E videos that Mercedes made Porsche change the intake tubes to include sound dampening as they were deemed too noisy by MB. So you're current setup is as Porsche had originally intended it
If you really, really need the original tubes I might sell a set. Will be in Germany starting Sept 8 and could ship them from Germany which would save you the U.S. shipping cost.