O-360 takeoff power fuel flow question

Hello

I'm looking for real-world data on full-rich, full-throttle takeoff
power fuel flow for Lycoming O-360 engines.

I have a C-172K conversion (Lyc O-360-A1A, Hartzell c/s prop and
PowerFlow tuned exhaust). The POH supplementals for the conversion are
a bit terse, but indicate that takeoff fuel flow should be in the
neighborhood of 18 GPH, with a stock Cessna exhaust. I seem to get only
about 16.0 =B1 0.5 with what I believe to be a well-calibrated fuel flow
meter (JPI EDM-700). I would expect the fuel flow to be even a bit
higher than the expected 18 GPH with the addition of a tuned exhaust.

Does 16 GPH seem too low? I seem to recall that O-320's burn about 16
GPH on takeoff.

Thanks for any info you can share.