I'd lean the engine out. 11.7 GPH on an O320 is a ton of fuel at 72% power on an O320. It's enough to support almost 170 HP, and you're producing about 115.
Does it clean up when you drop to 10-ish GPH, which is much more in line with a ROP mixture at that power?
What do your fuel flows look like at WOT and 65% power?