Gday, over the last couple of months ive noticed a pretty bad misfire at and above 4k rpm, which it will always do. I noticed after driving for around 3 hours last week the misfire completely went away, only to come back later. I've tried changing the coilpacks which i beleived could have been the culprit though with changing 4 out to rb25 packs which were working fine prior to me receiving them, i cant get any combination of coil- on plug to eradicate my misfire. I have just removed all the coilppacks and plugs, and ive noticed 1,2,3 cyl experiencing yellow discolouration at the lowest part of the ceramic on NGK platinum plugs, less that 4000 ks old. 4,5,6 cyl plug seem in much better condition, though cyl 2 plug having experienced the worst of the lot, with the yellow looking more intense, resembling sunburn-orange at the lowest point. This leads me to believe cyl 2 must have had the worst of the misfire, with possible misses coming from 1 and 3, as those 3 coils have all had more heat delivered to the ceramic. Those coils have all been replaced, with all combinations of coil i have (10 in total) having been tried. I was running 14 psi with no issues for 3 years, and after noticing the misfire i have wound it back to the lowest possible, 12 psi, though it dosent make a difference 12, or 14. Up to 4000 rpm the car is fine, idles fine and no smoke. The issue could have originated around the time i originally changed the old plugs, which were iridiums. Anyone got any ideas to solve my misfire issue? Ta