What are you driving? Accord f22 v-tec kicks in at 2200 rpm for example and works in a completely different way than say a b16. usually factory is best because without forced induction the car is not moving enough air to use the big cam lobes well until higher rpm's. Of course frankensteins are a different breed since they use bottom ends that never had v-tec. Then it's definately a dyno job.