We have found that the stock valve springs can be inadequate with certain high-lift camshaft grinds, especially when combined with a hi-revving application.
If the valve spring is not strong enough to to control the valve, it may allow valve toss* or valve bounce*. Either of these will reduce HP, and can exacerbate the valve keeper to the point of failure.
On the other hand, valve springs that are much stronger than they need to be add unnecessary loads on what is already a long and highly loaded cogged drive belt. The answer is valve springs that are "right sized" for the job.
The High-boost valve springs we developed for ourselves a year ago when we started running 17 psi of boost with hi-lift cams at the same time.
But, customers asked for a set of similar valve springs for their naturally aspirated race engines, and now we have them in stock as well. Note that we provide new spring cups for the high-Rev springs to increase the lift available before coil bind.
The webpage will tell you more, and let me know if you have any questions.
* Valve Toss: when the follower is thrown off the nose of the lobe, allowing separation between the lobe and follower.
* Valve Bounce: when the valve bounces on its seat when it closes.