  New vector bosons that are coupled to conserved currents in the Standard
Model exhibit enhanced rates below the electroweak scale from anomalous
triangle amplitudes, leading to (energy/vector mass)$^2$ enhancements to rare Z
decays and flavor-changing meson decays into the longitudinally polarized
vector boson. In the case of a vector boson gauging $U(1)_{B-L}$, the mass gap
between the top quark and the remaining SM fermions leads to (energy/vector
mass)$^2$ enhancements for processes with momentum transfer below the top mass.
In addition, we examine the case of an intergenerational $U(1)_{B_3 - L_2}$
that has been proposed to resolve the $(g-2)_\mu$ anomaly with an MeV scale DM
candidate, and we find that these enhanced processes constrain the entire
parameter space.
