After further research, I found this from an australian forum
from: http://www.performanceforums.com/for...-67221812.html

Quote Originally Posted by Ben Wilson View Post
Holden reckons they had a big batch of faulty cats, that started to disintegrate.

Under high engine vacuume conditions (ie closed throttle gearing down when coming up to a corner) little particles of the disintegrating cats would be sucked up into the engine via the EGR valve, then the pieces of said cats would start carving the crap out of the bores, killing any chance the rings have of sealing.

The fix is new motor, new cats, and new ECU programming to change EGR behavior under the above conditions.

And yes, Rodeos are crap.

The EGR pickup is close to the cat???