Ok, the new CCV assembly arrived and was fitted by me.
Everything was sealed and working properly; I cleared the codes again and then drove to my daughters home in Gympie Queensland (about 1200K's) from where I live.

About half way up the CEL came back on, this time it was only the 29f4. I cleared the code again, finished the trip up and drove around for the next 8 days with no CEL and no smoke.

Yesterday, I left to come home, started the car and the CEL was back.
I continued to drive home, the car drove flawlessly, no smoke, lots of power, at full throttle it runs cleanly to its 6500rpm shift points and good fuel consumption.

When I say no smoke, the car has always started without any smoke but before I replaced the CCV assembly it would start to blow oil smoke after 10 or 15 minutes of idling when hot. After I replaced the CCV assembly this gradually reduced and I did'nt notice it at all when in Gympie. Also the exhaust pipes had a sooty black look and texture before the trip, but once at Gympie they were largely clear.

As for fuel economy, going up I was pulling a loaded trailer and the rear seats were folded down with more cargo, all in all about 1.5 tonnes of extra weight. I averaged 15.8 mpg for the trip up, traveling at the legal speed limits. Coming back the car averaged 26 mpg. I did'nt check the fuel consumption while travelling around Queensland, but it seemed pretty good.

All of this leads me to think that there is nothing wrong with the engine or cats but that one of the o2 sensors is crook, but i don't know which one. I have after arriving home since cleared the code again, but would like a permanent fix.

I assume 29f4 refers to a specific o2 sensor, but which one?
Also is there a way to test the sensor before I replace it ?

The car is due for a registration inspection in May and I would like it to not only pass but actually be ok.

Any help or advice would be greatly appreciated.

Mike