basically how common was it, and how much more did it cost?

(in 1996) The Y87 Performance Package was available on the Coupe & RS, which consisted of four wheel disc brakes, 3.42 axle ratio (A4) [3.23 on M5's] and the sportier suspension components that the Z28 received. It required the P235/55TR16 tires (QBC). 2412 v6's were sold with the y87