*sigh*
Undamped pulleys put uneven stresses on your crankshaft.
If you want to make more power, you want that power as even as possible, because the more power you make, the more stress you have on your crank shaft, the more stress on your crankshaft, the more stress on your bearings. The worse the vibrations on your bearings and crankshaft, the sooner these things wear out and break.
Yes, with a lighter pulley, it will allow the engine to accerlerate and decellerate faster. If you are going to have a track *only* car, then this is a good thing. BUT, you will be rebuilding your engine, far more often.
The stock damped pullies are quite good. They are damped for a reason.
The new MZR engines from Mazda have balancer shafts, they don't need as much damping, and will benefit from a lightened pulley. Not so with our mazda F series engines. The F series from Honda have a balancer shaft, you can get away with a lightweight pulley there.
I'm telling you, it is a bad idea.
IF you are going to do it, do it right.
Don't put a $90 part in, which will cause a $700 rebuild. It's just not a good idea.
Sure, you can run with a lightweight pulley, for a while, but it will damage your bearings, and it will reduce the maximum amount of power that you can safelty make on a particular engine.
Here is a nice description,
Harmonic's In The L Series In-line 6 Cylinder Engines
but realize, they are talking about 6 cylinder engines, which are inherently balanced internally, much like boxer style engines.
For more good information about engine smoothness, and why and which engines are and are not balanced see:
AutoZine Technical School - Engine
for four cylinder engines specifically:
AutoZine Technical School - Engine