i have a 99 ls with 90k miles on it.....i already have a good suspension setup and wheels with sticky tires, the next thing on the list is a good header like rage or itr, high flow cat, and an exhaust like the rsr exmag...after the exhuast, are cams the next best upgrade, if so would my car need an upgraded valvetrain?

 

def to cams and yes Valve Springs & Titanium Retainers

 

Get the bolt-ons. If you want to get cams, it also depends on how aggressive they are if you need to upgrade your springs/retainers. I would do it though.

 

ok, i know the good headers like smsp, rage, and hytech, but how much more whp will those top of the line headers give my setup over a dc jdm 2.5 or an itr 2.5 header?? and how much over just a regular dc 4-2-1? thanks in advance