Second Loop Corrections from Superheavy Gauge Sector to Gauge Coupling Unification

We deal with extensions of the Standard Model by adding horizontal interactions between particle generations. We calculate two loop corrections caused by the presence of coupling between hypothetical horizontal gauge bosons and matter fields, both at low and high energy. It is proved numerically, that the coupling of such extra bosons does not affect the positive features of unified and extended standard models with horizontal symmetry discussed in former publications.