Thanks all. Spare AFM might be useful Mowgli just to reassure myself, I'd have thought the flap opened even when stationary.

One thing I forgot to say was previous owner thought removing the intake pipe with AFM attached from the inlet helped it run.

I had to chuck some fuel in to get it to run this well, so I guess there could be a leak or something causing the pressure to drop. It'll sit there ticking over for 30 seconds without revving though, and when I ram the AFM open it'll happily rev right up and not cough and splutter, so I assume it's got enough fuel and it's purely air intake issues?