Jay not allways true ,but there is no power from those plugs
most people that install new plugs and then dyno dont understand that just being a new plug will make beter power
this is the way we test spk plugs
we buy a new set of what ever the customer is running then we do 5 passes back to back this it to put the plug in to a heat cycle ,then they cool down for 10 min. then we do 3 runs back to back
then we change to what ever plug the customer wants to test and do it all over again
the only spk plug we have EVER seen a gain out of was the autolite AR series
we have found that the cheep plugs make just as much power and gas mileage as the higher price ones
I just did an artical in muscle mustand and fast fords ,i think it was in last months and covered some testing on a mustang with the autolite spk
plugs
Now as you move up in HP you need to step down in heat range and no one makes any for this
i sold justin(tobyboom) a set to test with and i have a set and saw 6hp out of the colder plugs on my car
spk. plugs can make some hp but the denso will only cost you more money buy the cheeper plug and spend the money somewhere where it will help
tom