The engine is the same internally. With the '10 model Mazda did take some of the edge off of the low end coming up on boost, as Darth pointed out. Otherwise the engines are the same. They's also played a little bit with variations on the turbo over the model years to try to address the "smoking turbo" isssue they have been chasing on some cars. But turbo seal issues are not blowing the engines.
My own personal (unverified) theory, shared by at least some others, is that that huge low end torque spike may be responsible for some of the failure. It's not good to go WOT on this engine down below about 2,700 to 3,000 where that big torque spike appears. Whether that's the problem, who knows?
I think a lot of those 07-08 blown engines were on cars that were modded and "tuned" in irresponsible ways and then driven carelessly. I also think there are some owners who don't realize that on stock tune the engine runs out of steam at 5,500 rpm and they are trying to zing the car to redline like a Honda. This does not make more power and can actually cause harm if constantly bouncing the revs off of the limiter. And finally, careless shifting can cause serious damage from over-revving the engine if a shift meant to be an upshift at high rpm ends up catching a lower gear. That's why if you always shift not higher than 6,000 rpm, even if you make that screw up, there's enough head room (mechanical gearing change would still have engine crank speed below 7,000 rpm), to keep you out of trouble. All of these are things that happen when drivers move into a new model, especially if they are relatively new to high performance cars, not familiar with stick transmissions, and are making mods to forced induction engines.
We've learned a lot over the last 3-4 years that the car's been out. Most of the failures are going to be due to owner abuse of failure to properly maintain the car.
