In terms of clutches it is really hard to beat the original product.If your setup exceeds the limit of the stock clutch(ie-clutch slips due to too much power),you have no choice but to look into a clutch system with more clamping force.
In the case of camshafts or exhausts, if you want to put more power to the ground,you need to get more air flow through the motor.Then you have to find a product that will really work.(plenty of products on the market that will hurt the cars performance)
Thats when you arrive at ignition system. Most of the time ,the aftermarket ignition systems that I have seen dont work.
When you change a part you want to see results.
Just because someone sells a product it does not mean it works.
Im talking about my experiences,others might have thier own opinions.You can listen to all different opinions then choose your own route
Thanx Rob