The fog lights use a single filament bulb. As such there's no way to have them lit and then get brighter as secondary stop lights when you step on the brakes.
By using the diode mod
, which is essentially a one-way valve, the stop lights don't come on when you turn the fogs on. The rear running lights are not affected. Using just a paperclip or wire splice, the stop lights would come on whenever you turned on the rear fogs because current would backflow to the stop light filament.