Running problem, wierd noises but not stalling

[Chidub]

My mk3 driver has always had a funny idle, however, it hardly stalls. The idle isnt to low, it just messes around 1000rpm...sometimes above it, sometimes below. Also, sometimes...when I hit the throttle it makes these wierd sucky, pop noise. Like the opposite of a backfire!?!? Thought it might be the rubber mounting between the injection manifold and single point but I've replaced that. Could it be the injection manifold gasket??? How do I tell? (apart from obvious things like blowing air etc)

[boneybradley]

Breather hoese i reckon....best one to try is round the back of the engine with a green valve in it... have a feel and see if it idle's better without the sucky noise