Your friend's wagon runs good with a 2.6" opening. EFI can't tell if the intake is restricted, or if you aren't giving it the throttle, it won't flood like a carb. Up here in the frozen tundra, the air cleaner often plugs with snow, and the revs come down like you let your foot off. The engine runs fine, just won't rev up. Dig the snow out, or sit and let the engine heat melt it, and away you go. I bet if you opened the 2.6" up, you'd notice more power.