Yes, some Porsches came with them from the factory e.g. 928S4
If factory fitted then they are road legal, otherwise they aren't.
"For track use only" I've had no problems with thin spacers.

Whatever you do, DO NOT USE STUD EXTENDERS (the hex type that screw over your existing studs).
They are made of cheese & can be stripped easily, even by someone with office hands.

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