I am running one on my 440 dually I cant tell much difference on idle quality . It does start better and response seems better. I can definitely feel the difference pulling the enclosed trailer.
I was just looking the truck over today getting ready for Monster Mopar,the plugs look cleaner than I'm used to seeing in a street vehicle.
I had to pull a couple degrees of timing
out with it to get rid of some pinging under heavy loads.
Keith