Possible air leak?

[Matt]

Hello, I own a '96 Bravo HLX(1.8) and when its cold, the idling is very dodgy and the engine really struggles(so much so im scared she'll cut out, so set some revs). When first started, shes fine though, but if i drive just to the bottom of my road say and wait at lights it will happen... When warm though shes fine again.
When i had the cambelt changed recently the mechanich said he thinks that air is escaping somewhere (gasket on something I think he said), does this sound likely to be correct?

Thanks Alot, any help welcoime, Matt.

 

[Tom]

When were the plugs last changed?

Air leaks would show at all RPMs.