Yura, It's not fair to blame the chip or it's tuner for the change in AFR after mounting a different exhaust and a different exhaust manifold. The only one to blame is you, because you changed the exhaust and the manifold.
No chip for a Weber-Marelli computer can be setup to cope with exhausts ranging from 60 to 80 mm. It works either with a 60 mm exhaust or it works with a 80 mm exhaust.
Get your chipped remapped by somebody who knows what he is doing.