Would it help if you ran some sort of beaters in that huge plenum to keep the fuel aerated? Two Kitchen aid beaters at each end of the box, 4 total, literally mixing things up, electric powered?
Would DI engines still have fuel backwashing up the intake ports out of the chamber?
Yes, I believe even with direct port injection, some backwashing would occur. Consider Kaase's finger as it is pulled up AND down as the valve opens and closes. Pulsing is an effect of the valve's opening and closing at a rapid rate. When the valve is snapped shut, that column of air/fuel it still moving towards the backside of the valve at high speed. The collision to some extent causes backflow (or back wash) until the valve reopens.
As Jay mentioned earlier on "....What gets me is the strength of the pulses; I had no idea they were that strong. When I switched runner lengths of the intake on my SOHC, I saw a huge power increase at the engine speed of interest, so there was evidence that the induction tuning really has a major effect. But to see Jon's finger snapping back and forth like that in the port really drives that point home."
Adding longer or shorter ram tubes on an fuel injected engine, like his SOHC in the '63 Galaxie, is a well know tuning trick to essentially move the rpm band up or down, short being up, long being down. However, I never really thought about how a long ram tube (for low-middle range strength) would coincidentally keep more of the air/fuel suspension, and not just the air, closer to the intake valve. I'd venture that if the runners in the plexi-box were say twice as long as depicted even less of a sheet or wave of raw fuel would accumulate in the plenum section.
And yes, Yunick is still long dead as are many of his disproven theories. The good theories and facts did survive him but have since been supplanted or added to by facts modern race builders like Roush, Penske, Kaase and other giants of the trade have proven time and again.