AFR misleading? Plugs tell a better story?

Thumper/whiplash is for sound and that means overlap and reversion at low rpm. Dual planes require split jetting to even cylinder feed if you really want to even AFR to each cylinder. That means the idle, cruise and WOT may require tweaking. Also when reading plugs you need to look at the paired cylinders. On an airgap it's 1&4, 2&3, 5&8, 6&7. Follow the runners and you can figure out the pairs.