Alu crank pulley.. are they good?

[vlgi]

Today's cars when engineered are often engineered so well that the room for tuning improvements are negligible.

A good example is the S2000, the engine is really an amazing piece of work and it is probably running at its limits, a lot of aftermarket add-ons actually decrease its performance because it is already tuned so well.
Also because it is at the limit by design it means making modifications is potentially dangerous because compared with a car which is not tuned heavily there are engineering tolerances to allow the car to run with less that perfect situations.

When you tune a car you are essentially using the built in tolerances that engineers designed in to ensure it would run well, as you reduce these you increase wear on the engine parts. For every upgrade there is a negative effect as well as positive.

The question is whether the disadvantages outweigh the benefits. For a stock car from the factory the suspension is designed for ride quality more than handling, so you can sacrifice ride quality and get better handling, engines are generally designed more for longevity than performance, you can get more performance out of them but its likely the engine won't last as long.

When engineers in motor sport design a racing car they don't design it to go 100,000 miles maybe a thousand miles, but the requirements for a race car is different from a daily driver or so on. As mentioned above, they have teams that can strip down a car and recondition it often.

Everything is about balance, there are no magic ways to improve a car without having some negative affect as well.