From AMuS' preview:
Imola is one of the power tracks on the racing calendar. According to Mercedes, only two other racetracks show a higher percentage of full throttle this year. From the exit of the last corner to the first braking point before corner two, the engines run under full load for around 15 seconds. Anyone who has too little power here and drives with wings that are too big will be punished.
Interesting - I wasn't expecting this. Honda could further stretch its legs if Merc hasn't fixed its derating issues...
Red Bull's lead could be even bigger in Imola. The Italian route is smoother and faster than Bahrain. The fast changes of direction in the chicanes and the high-speed sequences in the middle sector should taste particularly good to the stable and predictable RB16B.
I think this is expected, unless Merc makes a sizeable jump in improving the W12 balance. AMuS also states no meaningful upgrades for RB/Merc, only package optimisation.