Why is my lambda different in different gears?

97 Mustang GT. I'm trying to dial in my MAF transfer, and I'm getting different results when I do a WOT pull in 2nd than I do in 3rd. It's running a little leaner in 2nd. Also, there's a weird bump around 696 ad counts. It's rich on either side, but lean in the middle. If you look at where the break points are this doesn't make sense. Basically the peaks are at break points, and the valleys are in between. 3rd gear pull is at 3:20 and 2nd gear pulls are 5:20 and 9:02. Thanks
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You will be leaner in lower gears and richer in higher gears. Normally you will dial your fueling in 1:1 gear but depending on the vehicle, gears, driveshaft i may data log a gear lower. Not exactly sure what the science is behind it but load, acceleration rate, mph/wind intake could be factors, especially when maf based.