oh, i just call that the "big round hose thingie" anyway it appears to seal ok, n ive had WD40 round the whole seal n no change...

i'll try cleaning the thing out with carb cleaner 1st n see what happens...

the thing that gets me, is that i cant understand why it would do all this at idle, coz surely the metering flap is resing on the idle adjustment screw and so it wouldnt matter if the air goes past the metering flap or not