The airbox is the thing your air filter is in just behind your headlight under the hood. Big black pipe goes from that to your throttle body mounted to the supercharger.
The PMV is the pressure modulator valve assembly. Under the airbox, and has a small brake fluid reservior, a round pump body, and a manifold with brake lines. It'* expensive. We don't know if your failed relay is inside the PMV or elsewhere in the car. If it'* in the PMV, you'll have to either replace the PMV or live without ABS.
My PMV pump relay may be in a different location than yours, because my year uses a totally different style of ABS than yours. FSM is FACTORY SERVICE MANUAL.