The mic may be bad quality, but if you're surrounded by ambient noise, the mic CAN'T be smart enough to filter out the unwanted noise, and replace it with the good noise, in this case, your voice. Filling the cavity in the map light is only going to reduce the volume of all the sound that goes though it - it's not a cheap filter. The real trick is reducing the road noise in a loud car. Lets face it - the WRX is not a quite car and the mic is going to be picking up all that noise at the same time as it pics up your voice. A directional mic would help, I guess, but there's no replacement for silence to begin with.