I purchased my RX8 about 2 months ago, and after troubleshooting my low gas mileage issue thanks to info on this site, i brought the car to the dealership. They told me that rotor 2 was misfiring and they would replace the engine.
I brought the car back a few days later, after the received the engine, and they swapped out the motor.
Once i got it back, i could feel the engine rumbling, and it has gotten worse over the past 2 weeks, so i brought it to the dealership today. They tell me that the motor mounts are cracked, and made it clear that they weren't cracked 2 weeks ago when I got the car back. Has anyone ever heard of this happening? Could this be a result of an improper install? or is it more likely that the mounts were shot and they didn't say anything?

any ideas?

 

Likely the later....

 

most likely it was already on it's last legs (engine mounts) and new engine install just make it happen.

It's a wear item and you should replace it every few years. this is not just an RX8 thing, it's the SAME for EVERY OTHER CAR.