Where r u guys running ur illumination wire on ur stereos to? Can I just leave it unhooked? I believe it's just for dimming right?

What radio is it?

Depending on how old it is, it may literally be an illumination light, meaning it turns lights on inside the radio when the car lights are turned on. Those are normally solid orange.

The ones that actually dim the display on the radio when the car lights are turned on are usually orange with a white stripe.

you can tap into any gray wire going to a light bulb, like the console light or the heater controls light. or you can go into the gray wire going into the #5 port on your gauge plug-in

Ok thx. And yes it's a brand new stereo, USB blue tooth all the new stuff the ole 2 knobber didn't have.
Ps. Stuffin 2 5&1/4's in the dash was challenging. :p