You asked if one spark plug on a V8 would be noticeable. How about FOUR spark plugs not working? The Chrysler Hemi, for example cuts off four cylinders when they are not needed, and the driver does not know the difference. Of the dozens of cars I have had since my '54 Lincoln convertible, only about 4 of them have been imports. One British TR-3, two Toyota Cressidas, and one Toyota Supra. IF the car could not do 115 on the highway, I did not need it. Although I did dump my '60 Lincoln because it only wanted to go straight on twisting roads or sharp curves. That is when I bought the TR-3.