Ignition timing bang on? Not just cam timing..

The fact you cant blow through it shows the diaphragm is in tact which is good so that wont be leaking.

You need a co2 meter (friendly mot station) to set the fuelling but i'd only set this once the ignition timing is set also (12degrees btdc for a standard engine on decent fuel will be fine)

The HT leads wont be causing it to stall on coast down like that -worth replacing anyway if their breaking down tho! PS: HT shocks hurt don't they,lol