Ive just switched to a BCR8ES on mine. Although as yet, still havent had an opportunity to put the foot down. Probably very similar to what you are using. Just a plain copper, retracted nose plug.

i'd previously used PFR7B and BKR8IEX....but it seems sensless using expensive plugs in them. They also seem to be fairly fragile ( or maybe I just break them lol )

 

I have a cdi ignition and they say you cant use a resistor spark plug ie r

 

True, although Ive a couple of firends who ran MSD DIS-4 on their Subarus, were using NGK Racing Iridiums with no problems.

Nice plugs, but far too expensive for my liking.