I am in the process installing GT3 seats and roll bar in my 02tt and I have read several how to's, but nothing describes dealing with the Black plastic box that is mounted under the drivers seat. The It has 2 connections from the metal box mounted on the floor. My car currently has stock unheated comfort seats.

The passenger seat has only one connector from the floor to the seat belt recepticle and no black box, very straight forward.

What is this box?
Does it need to be reatached to the harness and relocated under the new GT3 seats , if so it looks like a huge PIA.