Have you tried the mount on your car? I just bought the #3 mount as well and was told the only difference was the compound of the rubber used. When I push on both of them the mazdaspeed one was harder to push.
Here is a quote from another user of the mount from another board.
I just installed the MazdaSpeed #3 engine mount today... wow, what a difference it makes to the vehicle's dynamics! Heel and toeing to 1st gear never has been easier! No more lurch and bunny hopping on first! Well, there's still some if you jab on the throttle, but that's a "normal" thing for a torquey manual tranny car Chirping 2nd is so easy now; I couldn't before because of how grippy concrete roads can be. Chirping 3rd happens now if I don't go easy on the car too!
The #3 engine mount is the mount at the passenger (right) side of the car. This mount was changed on the MSP to handle the higher power output. Comparing the MazdaSpeed mount and the stock mount is like night and day. The stock mount flops around, but on the MazdaSpeed mount, it takes muscle power to actually get it to move a bit!
The mount is identified by a blue paint dot on the metal bracket and the rubber piece. The stock mount has a white paint dot instead. This MazdaSpeed mount also has a "B26K" stamped on the rubber.
This mount makes a difference and offsets the load caused to the #2 (front) engine mount by preventing the engine from shifting back and forth unevenly at different rates (in otherwords, the engine likes to twist side to side in addition to the normal back and forth motion). Now that everything is stable on the car, transitioning into a corner is MUCH easier and I find myself from braking, entering, and exiting a corner process MUCH faster. And the beauty to this mount is, I don't have to put up with shaking my fillings loose with urethane mounts!
The part number is BP7H-39-06Y btw... and it costs just the same as what the POS stock mount will cost... about $140 retail... NOTE: it will ONLY fit 2.0l manual cars!