You will mostlikely get CEL if you're a 2000RS or 2001RS.
If '98 or '99 you'll be fine.
Mine is a 2001RS.
But I've taken the extra step to ceramic coat the headers and have the ECU tuned by Yoshio. I think the car now recognizes my headers & exhaust as a "stock" part so no CEL. Tuning is recommended, you'll even notice a difference in sound once your setup is tuned not to mention the much smoother power that comes with it.