I see this all the time and am baffled. Guys come to the track with basically good cars and "it made 900 hp on the dyno" engines and run 12s. Meanwhile my under 600 hp car runs deep in the 9s and I'm thinking, how fast would I be with 900 hp? Got to sort those rigs out if you want to be fast! More speed parts isn't the answer - tune the ones you have; work the combo. But that takes what has been alluded to throughout this post - you need to know how and why things work to in order to tune (or even simply repair) them properly, and that's acquired by experience.