Focus rs mk1 originally when cold would go to a very low idle almost to cut out but it now cuts out when cold or hot, start it strafing up and it fast idles but soon as throttle is touched it will rev then cut out, is there a common problem to look for, any advise greatly appreciated

 

air leak ? check the back of the inlet manifold for split pipes

 

my lad had this on his last week. cleaned out all the idle control valve and throttle body, now it idles perfectly

 

As said above check behind the manifold and the pipes that go into the white one way valve, also can you hear any hissing?

 

Idle control valve was the problem, thanks for the replies