I blew my engine. It always received a good warm up before MOVING, received regular maintenance from MAZDA and had an intake/TBE/BPV/Cobb AP.
I think the most common factor among the blown engines is the Cobb AP or similar off the shelf engine map. I have been running my car with the same mods minus the Cobb AP since I got it back and it has been bullet proof.
I think bolt ons are fine. If you want to make more power/consistent power or add any serious mods, you should find someone who can make a custom tune. Avoid OTS maps at all costs.
I believe that many of the "stock setups" that have blown were either negligence on the owners part (ie: lack of maintenance, etc) or they aren't telling the whole truth. Prove me wrong if you disagree.
In short, I blame most of the blown engines on the after market world, and peoples lack of understanding about how the car reacts to playing around with it. I was one of these people.
Bring on the flaming