So I have a 2009 Mazda6 with the push button start, 4 cylinder, I believe it is the ISport or Touring. Regardless, we bough it brand new in 2009 and have been plauged with exaust issues that Mazda continues to fix. So far 2 catalytic converters, numerous other modification and fixes. It has been fixed 6 times with more to come (just give it 6 months). The car has 72,000 miles on it. Now the new problem is the key symbol with the "!" symbol thru the key is displayed on the dash, the push button door locks on the exterior door handles no longer function, and only the driver's side door will open with the remote regardless of how many times you press the button on the remote. The vehicle just cost me $450.00 for a new alternator (was at work and was unable to get home to turn 2 bolts and clip in a electrical connector). Anyone having these same issues? I was also told by the independent repair shop that the diognostic showed power spikes to the instrument cluster. Any guidance would be appreciated. I can say Mazda Corp has not impressed me and I feel certain I will not buy another Mazda due to the milage and history.

 

1 thing Mazda never does is change the PCV valve. A faulty PCV valve over time could lead to excess oil going through the system. Make sure this is done.
However, this goes back in to the intake. It could lead to fouling of plugs and misfires which could lead to catalytic issues. I don't know how long this process takes.
I'm not saying this is the reason for your failure, but that it should be changed.
Piston rings worn could also be a reason of failure.