I had the NGK 1-step colder plugs on it before and still saw some knock in high gear durring acceloraiton. Also i liked how the gap is pre set on the denso, so i thought i would give it a try. I also have plans to add some more power so i though it could not hurt.
So I may have dropped the ball. I installed my ETS 3.5 about 2 weeks ago and am lovin it. I haven't heard any knock... then again, I haven't exactly been going out of my way to listen for it. Either way, I regret not changing my plugs... even just for the sake of it. I'm still gonna do it... but seriously, how necessary is it really? There's no mention of it in the installation manual so this is the first time I've heard of this.