Look below for the link that is all you need.Vibrant Race Header with high flow cat to help you pass emissions without issues and keep the CEL off without the need of a spacer the O2 sensor.That is the only header for the SI that I know that comes with a High Flow Cat. With the other ones in order to prevent a CEL you will need to add an spacer between the O2 Sensor and the Header socket to separate it from the exhaust stream preventing a CEL coming on. That is my case with mu DC Race Header and so far has worked very good that spacer no CEL for more than 2 years on my 06 SI.































www.corsportusa.com