car made 350rwkw at 20psi on street tyres rsr's and the 2530's
same tune, same car, same dyno but with a set of "r spec" handcock 221's c70 softs and it makes 310rwkw
still felt like it had 350rwkw (Duncan my independent tester can confirm it was a healthy 310rwkw) so i think the r specs suck up some dyno powers.... they also melt after 2 runs.
either way the above dyno graph is on the same dyno, same rubber and same fuel( had not even emptied the tank since it borked the gearbox... so a fair comparison i guess