Yeah ... you have a bit of a hybrid system and it all started by whomever changed the original single piston calipers to double piston calipers ... Can you get a hold of the previous owner and ask what happened to the OE calipers?

If you can get the OE calipers (and brackets and make sure they come from a 4.8i!!) you can use the rotors and pads I have (cheap!).

I'd go back to the OE setup if I were you ... keep it simple.

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PAX5
BMW CCA #20645