Ive had a few cossie's now and i must say that plugs that have worked fine in one didn't in another, however these denso ik31's on my stage 3 sapph work great and without advice i would have just stuck some more pp8's in as i agree that if it ain't broke don't fix it, it now drives better than ever, i even had a strange boost problem that nobody has been able to trace and that's disappeared so maybe it was something else, very happy now.