Hi Ben
Your symptoms sound very similiar yo the problem I had with my last car, it's gone now, only had it 4 weeks after the 'fix', which in my case was cured by replacing the turbo.

Have a look in this thread

Hi, thank you for that!! I really hope It doesn't come to that. As I already see I got a fight on my hands from the dealer I got it from. I'll bare that in mind if the problem persists and this air flow meter isn't what was wrong.

Fingers crossed.

It took 7 weeks of attempts by the dealer, they would try something and it would stop, then days later manifest itself again, they changed loads of sensors, DPF, EGR and eventually the Turbo, there is a Silver GS out there with lots of new parts, waiting for it to pop up on here. PF 11 EZT.

Good luck with your efforts and I hope the dealer perseveres with it and resolves the issue.

UPDATE: after 5 days and plenty of times starting the car, the issue hasn't shown its face again! Still early days but it's looking like it's fixed. It pulls like it should and it feels much better! I'm happy with it now. Thank you though guys for your help and advice. Much appreciated!