Is 100*C a problem? 120*C is overheating. 100*C is 20*C away from overheating. It's normal for the engine to run warmer during Italian tune-up than it would cruising on level ground. Maybe you're used to the typical damped and normalized temp gauges that don't fluctuate so the typical driver doesn't think something's wrong.

Sixto
95 S420
87 300SDL