Comparison of the $\pT$-differential $v_2\lbrace {\rm 2PC} \rbrace$ of inclusive muons at forward (left) and backward (right) rapidity in high-multiplicity p--Pb collisions at $\sNN =$ 8.16 TeV, extracted with the two-particle correlation method with previous measurements performed in p--Pb collisions at $\sNN =$ 5.02 TeV for inclusive muons  and electrons from heavy-flavour hadron decays .