You have an 91ish Bianchi with SLX tubing? So does this have Chorus or Athena group?
It doesn't say so in your initial post but I presume your trying to install shimano brifters and derailleurs?
I suspect the issue is simply the mismatch of the CampI crank with the Shimano indexing front derailleur. You may need a newer shimano crankset.
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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