I agree with T-Mar the decals are wrong for '91 and I do not recal any 'off the shelf' Bianchi with Dura Ace. sice you do not know the year I assume you bought this used? do you exactly which components are "orginal" and which are replacements? the wheels do not match neither do the brake calipers.
as for the frame while the decals look like the ones used from '92 onward for most bikes the full lenght brake cable housing makes the frame look older. then there is the whole thing about the DT looking oversized and ovalized at the BB. that agains leads me to think a '91 and newer frame with SuperSet 2 design.
the paint is not off the shelf either. it appears someone repainted the frame to look like a '88 Trofeo in the Argentin colors.
what is stamped in the staycaps? is this a US bike? where do you live, could this be from Canada? what markings are on the dropouts and forkends?
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk