So, got a remanufactured engine after a few weeks of waiting. Apparently both the 4 cyl and 6 cyl engines are in short supply due to high demand-- of course Mazda still denies a pattern of engine failure.
Mechanic installed engine, felt front cats were plugged with oil so replaced them. Now he says the new engine is bad. Engine supplier says it was tested befroe shipping, will want to see and test this before shipping out another, which is moot since they have none available. Probably going to be at least ANOTHER six weeks before I have a car to drive, and have been without since December.

 

So, the mechanic reinstalled the precats w/o looking at them? How did he figure they were bad by being filled with oil after reinstalling them on the new engine? If they were previously filled with oil, he would ave definitely known this when they were off the car. Sounds like this is mostly turning out to be your mechanic & not so much of a Mazda issue. I wish you good luck with the new motor.