I found the RB74/Comp2 combo great at Wakefield, no real issues all day and I did almost 90 laps. I'm using DBA4000 slotted rotors front/back on my R33 GTS-t and they weren't dusty at all. They did squeel under light braking but were fantastic... when hot. For my 5km daily trips they were overkill so i've gone back to some cheap 2nd hand standard nissan pads which... don't have any bite but do work well enough from the very first stop.
Sounds like PI is quite a high speed trap... I think I need atleast 5 pairs of underwear for the day going on the speeds you guys were doing. In the wet you would have had to drag me into the car