Well, a workshop put some Iriways in there and it developed a big misfire on boost. Went to autopro with one of the Iriways and they gave me some BKR6ES-11 to try, I regapped them to .8 and put them in... still misfiring. Eventually I got splitfires but it was still misfiring with the Iriways, so I put the gapped BKR6ES in there and the misfire dissapeared.
My plugs were a bit fouled from when I played around with my AFM settings so I thought i'd try some BCPR6ES-8 (I think they're actually longer than both the Iriways and BKR6ES) and they work fine... No problems at all thus far.