I tried an Iridium plug which was specified by my dealer as being the NGK CR7EIX.

I found it to be sluggish and choppy, and if it wasn't a single cylinder, I'd have said that one of my cylinders wasn't firing correctly... It felt like that.

I saw someone mention the same problem and he swapped it for the next plug in series, the CR8EIX which I did and it's a perfect plug for my bike.

Maybe because the engine burns hotter with the mods I've done, I'm not really sure but this did make a noticeable difference to performance.

__________________
Bike: 2013 XT660Z, TKC70 tyres

Mods:
Barkbusters, Scottoiler, DIY Tail Mod, DNA Stage 3, Power Commander V & O2 Eliminator, Exan X-Black Stainless exhaust, Tool tube, Ohlins linear front fork springs, Nitron rear shock, JT front and Supersprox rear sprockets, D.I.D. VX 520 chain, Adventure Spec bashplate, DIY USB Outlet, DIY chain guide, Kev's Throttle mod

http://www.facebook.com/onemooseonemotorbike