i have a 06 civic si...i wanna hook it up so before i make it look good i want it to be fast...i wanna install exhaust, headers, and intake but i hear if i do that the check engine light coming on will become normal...is this true?

 

yes, it'll be the 2nd o2 sensor, which basically tests to see if your cat is dead.

You can buy an o2 simulator to make the cel go away.