I have two Griffin Gas Pocket BCG's (one "enhanced" with the shorter gas key for longer stroke, and one 'milspec').
They both, for me, 100% make a suppressed AR quieter. I don't think they changed my gas/overgas all that much, I'm currently running standard A2 buffers with Tubb FlatWire springs and with the suppressors attached, they're overgassed (or were, more below).
Both rifles, with cans, were overgassed. One is a KAC LPR Mod 2 (proprietary gas block/tube) with an OCM5 can, the other is a Bison Fulcrum (proprietary gas block, intermediate gas tube). The KAC LPR has the 'enhanced' GA GP BCG, the Fulcrum has the 'milspec' GA GP BCG.
Since the milspec GA GP BCG has the standard gas key, I replaced the key with a Rubber City Armory Adjustable Gas Key. The RCA AGK tamed the gas on the Fulcrum barrel by limiting the amount of gas that goes into the GA GP BCG and made a softer, more pleasant rifle to shoot. If I wanted to do the same to the KAC LPR Mod 2, I'd need to get a milspec GA GP BCG and swap the key on it. I don't think I will just yet.
I am running pretty spicy loads with 77gr SMK (also 73gr ELDM), AA2520 with NAS3 cases. I was getting odd fliers with the 73gr ELDM and gave up on them after a couple hundred rounds.
This delayed/gas/flier discussion at the beginning has me wondering, what if I shutoff the gas? Yeah, it'll turn it into a single shot but if the pressure/gas is causing the fliers, removing that might fix it? Or not. Maybe.
Just thinking out loud a bit. Something to try this weekend.