Thanks D360 - I'm not sure I want to go through all that agony

I've done the holes in the butterfly thing a long time back - but this is a case of lean running well off the idle and into the low speed circuit.

I might try reducing the air bleed hole size and see if anything improves -

Like you - I still can't figure if you are meant to enlarge the idle jets as well as reduce the air bleed size - hopefully Demon Sizzler will chime in again.

Id also like to know what the correct base gasket is to use.