Distribution of the reduced enhancement η₁₇₅ (resp. η₁₄₈) (Eq. (8)) of the DIB normalised equivalent width, EN, of all DIBs, χ_a DIBs and χ_b DIBs, in the sight line of HD 175156 (resp. HD 148579). Both lines of sight have four DIBs with formal values of η> 10.5 (Table C.2 and Fig. A.1). In panel (c), these distributions are compared with more normal EN distributions in HD 183143 and HD 204827, (see also Fig. A.1). The shift δ of the central roughly Gaussian distribution from EN_av (Table A.1) is also displayed.