By reducing the plug gap, the coils can handle a lot more cylinder pressure. Every little miss fire on a factory engine causes emissions they have to clean up, plus a touch of lost mileage. With that in mind, I bet they are as good as my 4.6 Mustang coils, and with tighter gaps those coils have handled a lot of boost. I run 7.5 PSI with the gap at .035, have for 50,000 hard miles.