I was told by a co-worker that a new Part 91-mandatory compliance reg
has come out, requiring all airplanes to meet a min. climb gradient of
2.5% for second stage climb gradient, unless published otherwise. In
other words, if no specific gradient is published for XYZ airport,
then the airplane must be able to climb out at 2.5% minimum.

I am unable to locate any regs or anything that address this, so if
anyone has further info and the reg, AC circular, etc, please let me
know

Thanks