I can't reallly pinpoint whether or not the denso's helped me out because I did denso's, 9mm ford racing plug wires, and ported LIM secondaries all at the same time, and upgraded to 2ga battery cables shortly after. But, it definitely pulls a little harder after 4k rpm, it starts a little faster, and on a recent road trip I got a little better than 26mpg with an average speed of ~80mph(traffic permitting) and several (n/a) WOT runs into triple digit speeds and even a few lengthy stop-and-go traffic jams on the highway. Point is, it wasn't ideal highway travel, but I still got decent mileage.
But like I said, I don't know what mods account for what gains because I did them all pretty much at the same time.
What I have noticed is that with the plugs one stage colder than stock the car doesn't really run hard until after it's warmed up, whereas before with the stock plugs I'd get the best runs when it was still cold. :headscratch: