Even for autocrossing I use blanks over slotted or drilled rotors. As you want MORE surface area not less for braking. Plus blanks are cheaper than slotted or drilled anyways.
For my autocross only car which I won 39 out of 40 autocrosses I was using Brembo blanks and AEM ceramic pads.
My 91 Civic Si was a momentum car, no need to slow down
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