I'm not sure this is an equivalent comparison, but I'm running a roller cam with nearly identical int/exh duration @ .050" through GLM manifolds and stock Merc stainless risers. It has a 114 LSA. I have not witnessed reversion in my set up, plus my wide band would let me know cause it's right there. But since its a roller cam I know the ramp profiles are much different than the flat tappet stuff so this may not be an accurate comparison.

I suspect the gasket between the riser and manifold is more likely the culprit.