im not haveing mutch luck with my ideling ?

my car ticks over dead lumpy just on tick over but if i drive it
eg when i come to stop and slow down it stays at 2000 rpm

its reail pissing me off

the crank case air flow sensor behind the manifold it a black box could it be this if i take the rubber vacume pipe off located on the right hand side on the manifold tick over goes worse but if i block the pipe with my finger it tick over normal

does this mean the black box thing is what i need to replace

im getting reail stuck with what it is plz help