Jim Parr in Texas has talked about making some TB anti-reversion plates. I am unsure what the status is though. We tested at least 4 different spacer-styles during R&D on an inertia engine dyno including anti reversion on line of sight manifolds and a simple open spacer was as good or better than anything - but I am not aware of any meaningful track comparisons. There could be something there, I just don't know.