John, I think it might be the idle jet itself being too big, but I haven't investigated just yet. I'm getting better at driving around it,instead of taking the car out of gear & coasting up to the lights, I leave it in a gear with the clutch out until I'm almost at a stop, then I blip the throttle with the side of my foot while braking. After 2 or 3 blips it'll idle perfectly. So I reckon the increase vaccum of a closed throttle is pulling too much fuel in & drowning it. Another hint is in a weber publication saying if the idle mixture screw is less than one turn out, the idle jet is too big, & the idle screw doesn't seem to affect the engine speed until 1/2 a turn from closed. I'm taking Saturday off, & I'll spend some time looking at all these things. I just hope the idle jet is the same sort as the A12 one, or I might have to resort to soldering up the hole & redrilling it smaller. Got some tiny wee drills that'll do the job, though they're a bugger to find if you drop them.