A few years ago, I tried E3 spark plugs in my Pagoda and the initial results seemed quite promising. Someone asked me today if I recommend them and the answer is a definite, "No". So I thought I should update the story.
At first the plugs seemed to be okay, but I ran into some irregular fouling issues. Because of that first blush of improved fuel economy and pep in the Pagoda, I tried them in a BMW E30 and A VW Golf. Neither of those cars showed any improvement in fuel economy or performance. After a few thousand miles both cars started to lose fuel economy and the BMW started having some peculiar misfiring. When the E3s were pulled, there was no obvious wear. I suppose that is because of their unique design. I've gone back to NGK in all of them and there have been no further issues.
I chalk up this experiment as a failure.