Erratic throttle response when cold

[HPsauce]

I haven't checked them for a little while, but they certainly were OK last time I looked and all components appeared to be in top-notch condition, free to move and moving as they should.
A job for tomorrow I guess, but wouldn't they be in the low-rev position at the start, or does that require the bellows to move them - I can't recall which way round the actuation process works.
Could them being in the wrong position (whatever that is) cause this, if so how?

Edit: Just been having a read how this works.
Engine off the flaps are open, giving the shortest inlet (suitable only for high revs)
On starting the vacuum moves both actuators, closing both flaps and giving the longest inlet, suitable for low revs.
So if I had a vacuum leak there could, as they say, be "unexpected results" due to an inappropriate inlet manifold configuration.
I've read a fair few articles/postings about replacing the vacuum pipes with more robust ones.