found some affordable headers LOL

Good class cars are expensive to build. As AbodyJoe says, those guys are looking for every last thousandth.
Plus, you have to try different diameters to see what works best. $$$$$$$$$
I would guess that about 3/4 of the class racers that I know have been divorced at least once.
Those classes have a lot of guys who have to have the best and be the fastest. That's where dial-in racing came from. Being the fastest is EXPENSIVE and would narrow the field considerably, if it weren't for dial-in.
As an aside, it's only fair to mention that there are lots of combinations you can build for Stock/Super Stock that don't require that kind of spending. There are guys who like to pick through the classification guide to look for combos with weak hp factors. Meaning, they can run under the index without extreme spending. Classracer.com is a good site to read what these guys are up to.
I grew up across the street from a Stock Eliminator racer. I've been hooked for 40 years. Raced for 3 years, been a spectator the rest. Still married. :D