Seems OK on light throttle, tick over etc. but when you floor it, and lean forward to cope with the G-force

Vacuum hoses look OK.
I’ve changed the accelerator diaphragm and this looks to work OK.
The dizzy vacuum advance works.
The secondary butterfly opens when sucking the diaphragm (with the primary held open). I’ve tried to get it to open by revving it and looking down the carb but it doesn’t move (I didn’t want to rev it too hard though).
Any ideas?