Plugs are very easy to argue over. I used to do a lot of serious autocrossing about 15 years ago and guys running in stock class spent a fortune doing everything they could to "improve" their stock cars. One guy did several days of dyna testing with his stock miata and Just about every plug known to man. The results. Indexing plugs so that the spark was aiming at the intake valve was the best bang for the buck with no appreciable difference between plugs. A whopping 1-2 hp change!
I read an article awhile back on plugs in sportbikes when I was making an attempt to become the next Rossi and after several syno runs with different plugs the only ones that consistently gave an extra 1-2hp over stock were larger dual prong plugs. The tuner was convinced this was achieved only by the slightly higher compression it created due to the larger size and protrusion.
Last time I bought plugs for the Max I picked up a dozen of these
https://www.ngk.com/product.aspx?zpid=9860 They have been working great. I indexed them as I do all of my plugs and noticed no difference in performance from a good condition non-fouled plug as is
usually the result.
