I seem to remember an article that described how a lightweight flywheel only gives you a noticeable acceleration advantage in lower gears (i.e. 1st and 2nd). Can't remember where it was (and too tired to think about the physics at the moment) but I'll try to dig it out.
Lowering the overall gearing is an excellent way to improve in-gear acceleration full stop. Don't expect any improvements in the favourites like 0-60, 0-100, 1/4 mile etc. ... in some cases it will make them worse.
To show the sort of numbers that a real car might have, I did some calculations based on a car with average gear ratios and tyre sizes - the table below shows the number of Kg of mass that would have to be removed from the chassis to equate to 1 Kg removed from the O/D of the flywheel at a radius of 5 inches.
GEAR MASS KG
So in first and second gear this is a pretty important effect - I built an engine recently and managed to remove nearly 3 Kg from the outside of the standard flywheel - so that would be equivalent to lightening the car by over 100 Kg in 1st gear - not to be sneezed at in terms of acceleration from rest. With special steel or aluminium flywheels even more moment of inertia can be saved. The recent trend in racing engines to using very small and light paddle clutches and flywheels is therefore more effective in terms of the overall performance of the vehicle than it might first appear.
Lightweight engine internals (Ti rods) and external pulleys have a similar effect to lightweight flywheel.
In US underdrive pulleys for accessories are very popular.
Unorthodox Racing and AEM both make them for the Eclipse 4G63.
Not sure if they fit the evo's - I can get the Mitsubishi part numbers for the Eclipse pulleys - can anyone get the Evo part numbers???