Changed to new wires and re-connect back to "multiplex" mode (proper wasted spark configuration) and richen up the fuel a little. Now I can pull cleanly to 6500 RPM
However, in trying different things, I am quite sure I have blown one (or more) of my ignition drivers
Probably because of the super long dwell (4ms) that I experimented with - heat probably killed the drivers as I'm now having occasional ignition drop out. Will have to replace them then test again.
Re:timing - as everyone suggests, I'm going to get her on the dyno to tune that. I have been waiting till I can at least run clean to redline before doing that. I picked 18 deg (@ >.6 bar & >4000 rpm) as one of my buddy with similar build (different ECU though) is running that for a few years without issue. Hence I used that as my starting point.