I tryed it on my 1995 Ford Mondeo 2.0 station wagen with a 2.0liter Zetec engine and 5spd.
MGF just went down very little, probably was more measuring tolerances than real gain. But I felt (maybe it was just a feeling?!) that the engine is stronger and revs quicker. A friend with the same car did the same, he also didn't gain mpg but also felt more power when accelerating hard.
So I don't really know if I should continue with that, but surely will try it this summer with my 440...