Had the same problem, followed resonating heatshield advice, exhaust brakets...nothing... problem got worse, booked in for due service and i mentioned a cautionary cambelt change, idea dismissed as unnecessary by mazda... service, then it came to driving it home, metallic pinky sound followd by jerk and then it died, apparently cambelt had slipped luckily mazda accepted responsibility and got cambelt change for price of the belt!

I agree, the first thing i did when i bought mine, even though the 54K service was stamped was have a new cam belt....it turned out that the old one was ok, but better safe than sorry.

if you have work done, then at least you know for sue where you stand, you dont have to go buy a logbook and what the previous owner tells you....