Emissions Workshop Light Code 16485 Mass Airflow Sensor (G70) Implausible signal P0101 3510 Intermittent

Hi all, I recently took a long road trip after months of local pottering around, the emissions workshop light came on a descent after a long hill pull, on for a few days then cleared itself after so many ignition cycles, came on again on my return journey and I cleared it with the laptop, and it has not reappeared since with local trips. I have checked for charge air leaks other than oil residue on the CCV pipe and the normal oil seep at the EGR nothing out of the ordinary. The exhaust has had bad fumes at idle but not smoking and mpg is down but I had put that down to the short trips, is driving and pulling well through the rev range otherwise. I changed the MAF with a new Pierburg sensor prior to the road trip, no specific issues with the old original Bosch senor other than car is 15+ years old and is coming up on 400,000km and I figured it was getting a bit tired. Has anyone had a blocked/restricted cat on one of these? 2005 1.9Tdi AVF Auto.

Edited 14 August, 20205 yr by gfinneran