I have an 03 19.tdi ASV engine. It has been down on power so I changed the MAF sensor and then I drove it afterwards it ran fine then twice it ran up to full throttle. First time I stopped & pulled the key and it stopped the second time it ran on. briefly. I've changed the MAF sensor back and it is back down on power. Does anybody have any suggestions.

Sticky anti-shudder valve?

Is there any evidence of an increased oil consumption?

sounds like you have an intercooler full of oil mate, I would drain it by removing the lower pipe and wiping as much oil out as you can.

Thanks for the quick replies. I'll take a look over the weekend. It's odd because it behaves fine with the old MAF sensor back on.

The MAF only measures actual airflow. The throttle position sensor should tell the EMS how much fuel to add, up to the limit of the current airflow. Accordingly, if you're getting a runaway, then the most probable causes are either the engine is burning lubricating oil (see #2 to #4 inc) or the TPS is faulty (needs VCDS or a second known good TPS to confirm/deny).