I ran some more fuel through the 160 today. I now have burned six 14 oz tanks.

For the last tank I removed the baffle in the stock OS muffler. Evidently the 18x6W is running considerably above the peak torque rpm for this engine, because I saw less than 50 rpm improvement with the baffle removed. I also tested with a Zinger Pro 20x6. It picked up 250 rpm with the baffle removed.
Both props lifted just over 18 lbs on my test bench, but the Zinger would allow the engine to throttle up noticeably quicker.
I am getting a reliable 1950 rpm with both props, and zero hesitation from idle to wide open. I have leaned the low speed needle about 3/4 turn from factory setting. I am still waiting for the Slimline Inverted Pitts muffler and Cline regulator to arrive.

Current readings from today (today was very overcast and VERY humid).
Atlanta, Ga. About 800 Ft. ASL.

APC 18x6W - 9000rpm - Lifted 18 lbs, 4 oz.
Without baffle, maybe 9050.

Zinger Pro 20x6 - 7650 rpm - lifted 17 lbs, 13 oz.
Without baffle - 7900 rpm - lifted 18 lbs, 2 oz.

Fuel is Cool Power 15% nitro. Plug is OS # 8.