were do i tap into the o2 sensor for the air fuel ratio gauge there is 4 wire i look but cant find it any were thank you this is my 06 sti

You can't tap into the front 02/AF sensor which is a semi-wideband and not compatible with the narrowband gauges. You have to use the rear narrowband 02, which is after the cats. Because of this, those gauges are worthless for accurate AF readings and will only provide a light show as you drive.
If your car is stock or only lightly modded you don't need this gauge anyway, if you do have a real need for monitoring AF you'll need to get a wideband setup with a separate sensor installed in the manifold.

^^^i no iam tapinging in to the rear 02 sensor but what wire do i tap into there is 4 wiresthank you

Ok then, as long as you're aware of all that-
I don't have the wiring info on the 06, so I can't tell you what the wire colors are for sure. I'm not going to give you what's in the 02 manual since it may well be different.

but wouldent 02-06 be the same aslong as they have 4 wire for the rear o2

bump please i hook it up to the white wire but nothing happen

i want to say its a purple wire, but thats for an 02 also. didn't do much for me.

cool i will try it right now

therer was no purple i tried whie and blue now there is only two black ones...