Ok I recently got a Strup header. When you install a header it kicks the engine light on because of the increase in exhaust passing through the system. To offset this you have to "trick" the computer into thinking there is less gas then there really is.
The Strup header comes with one but it doesn't work so well. You can purchase on from Weapon-R, but they are a bit pricey and I have been told they still have the light come on from time to time.

Described in this thread is how to make an el cheapo one that is supposed to work very well. I say supposed to because I haven't installed it yet and tested it out. I will update when I do test it out this weekend.

 First go to your local auto parts store. Pick up a set of anti-foulers. They are quick fixes for spark plugs that are found in the HELP section. Pick up the (18)mm size. The package should include (2) anti-foulers and costs about $3.

Take one of the anti-foulers and drill out the hole in it with a 1/2" drill bit.
Remove your secondary oxygen sensor.
Install the AF with the smaller original hole first.
Then install the AF with the larger hole you drilled.
Then reinstall your oxygen sensor.

Presto it should work. And if you have already installed the header and set off the light then do the following.

Unplug your battery by disconnecting the Negative terminal.
Let your car sit unplugged for (5) mins.
Then reconnect your negative terminal.

Again I will post an update after I test this for myself.