Getting a bigger header or using no cat. converter can affect to full performance of a SC of turbo...but if you want to add 5oo+HP...You will need to upgrade ALOT of stuff!!! Pretty much a whole engine rebuilt. Look around and see what you want...But it takes time and money, for performance. I'm just about done with my max (stage 4 ) upgrade on my SC...put in a lot of work and cash! But soon after is the dyno and will post those numbers on my garage! I'm hoping to get 450whp + or minus that! Good luck bud. Hope I answered some questions.

Hey sorry for the late reply...been busy. But mine is all stock engine...NO racing cams, headers, bigger injector’s, all full blown stock. At the time stillen and they still do! guarantee for their SC not to harm the engine...There are mods done on the CPU side to compensate for air to fuel mixture...also the stillen SC has a black box that has all the mod and can be programmed to get the most out of the engine! Pulley upgrades will also give you HP, I have Borla exhaust from the back of the headers to the rear, and the inject intake for cold air...I recommend and will not go past 7 Lbs. of boost.