So I’ve run into this before, and it’s a multi piece puzzle. You have floating calipers, which aren’t as rigid as a fixed caliper, your guide bushings are shot, and your guide pins are stripped.
Your calipers are definitely in need of a rebuild, and I strongly recommend you do them yourself. I rebuilt the 330i calipers I put on my sedan, and you can source the pistons and and piston seal from Rockauto, you want the centric brand for the seal. For the guide pins and bushings, you want to go to the brass guides. Bimmerworld and FCPEuro offer these, here’s a link:
https://www.bimmerworld.com/Brakes/C...-Calipers.html
The beauty of the brass guides is that they deflect much less under heavy constant load, such as a track environment, preventing your tapered brake pads. It’s about as close as you can get our floating calipers to fixed calipers.
I wouldn’t do another track event with your current brakes, and I strongly suggest you keep a dedicated set of brake pads for only the track.
If you have any questions on rebuilding them, let me know, I’ve done it a couple of times now so I’ve gotten pretty good at it.
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