Polo - Air flow sensor

[Evie]

I have a W reg (2000) polo, for a year or two i've had an intermittent fault with the engine idling erratically and losing power (when hot or cold). VW said they 'thought' it was the MAF sensor (air flow sensor), they said the diagnostics test wasn't actually picking up on any fault though. I've since taken it to another garage to try and get it fixed because it's much worse (revs are constantly up and down). They have told me that after ringing around they've been told that there is no such sensor on my make of Polo. Surely VW weren't wrong.. Is there a MAF sensor, does it sound like that's what causing the problems? Can anyone offer any advise?
Thanks