I have a trz dogbone rear motor mount installed. It's rough and it makes the car vibrate but it also made shifts more crisp and helped with the lack of torque while accelerating from a stop. The factory mount has a lot of flex to it and it absorbs some of your torque.
If ratles or vibrations bother you at all leave your mounts alone. The mazda3 WILL vibrate quite a bit with stiffer mounts installed.
http://www.protegegarage.com/1260-trz-dog-bone-rear-motor-mount-mazda3-and-mazdaspeed3.html
I have the polyurethane one.
Which one would be a better call? The TRZ is on sale for $99.99 right now, and the AWR is still $89.99. Should I shell out the extra $10 foe the TRZ? Is it any better than the AWR? I don't actually know how to install this either, I can do it, but I just dont know what the procedure is. IT seems pretty straight forward, as in remove the old one, and replace it with this one. Could you guys link me to a How-To?