Putting headers on the stock exhaust will not garner you the full gains everyone states.
Headers should be after exhaust (Y-pipe & 2.5" Quasi or true duals) & intake mods in the grand scheme of things.
As for your run in with the Hyundai. They should not be able to keep up with a stock SVT, much less one that is modified unless the driver sucks or the car is running poorly.
Close at first, but only through 1st or 2nd gear. Just like most other like challengers (light weight) in the high 15 range (Gen 3 Z24, Si, SVTF, Celica, etc)
