It is my understanding that you'll need a head Unit with the 6-disc changer & trip computer built into it. I believe the older system would work. I read that you could do that in the older head units, but they changed it in the 08's & 09's.
Yeah its a sport. I just thought Mazda may have fixed it to where sports won't give the trip computer even with the older 6-disk changers in there. Just because people were doing it in the 08's