The stock button only sprays for 4 seconds and then you have to hit it again.  This one stays on till you press it again.

How-To Mod JDM STi Auto Intercooler Spray button to Light Up

Info:
For you that have the JDM STi Auto Intercooler Spray button.
This is how you make it light up orange when spraying.
I got the part for $39.00 shipped.

Parts needed:
1. Thin Wire.
2. Soldering Iron.
3. Solder.
4. Electrical Tape.

How-To:
You basically have to ground the light bulb since pressing the button supplies 12 volts to the top light bulb but isn’t grounded.

1. Shave some plastic out to fit the small wire like in the picture.
2. Solder the top metal to the bottom metal like in the picture.
3. Wrap with electrical tape.

Done…Enjoy your new orange light.