Fortunately I had a customer who was patient and in no particular hurry.
The problem seems resolved!
I finally bit the bullet and removed the camshaft carrier.
Although seemingly clean inside, many of the hydraulic lifters had in fact locked solid. I gave them all a squeeze in a vice to get them moving again and now reassembled emissions are now all spot on!
Basically what we were looking at was tight valve clearances.
Unfortunately the design of the AUS engine makes easily checking this difficult.
But, once you bite the bullet, it isn't really that hard.
I would suggest doing the lifter squeeze as a matter of routine with a cam belt change on this design of engine. It would only add an hour or so to the job (if that) and represents good preventative maintenance on older vehicles that might have had irregular oil changes in the past.
HTH helps somebody else in the future!
Regards,
Paul
