Sorry to dig up an old thread. My current pd160 has just started with this issue aswell. Going to 1k revs and down to 800/850 every time I start it in the morning. It’s fine when it warms up however, after a drive to work etc. Tried unplugging the MAF and also checking fault memory, no stored faults. I’m baffled as surely If there was an issue with a vacuum line or boost hose it would be constantly hunting? Any
help appreciated lads.