John_Yossarian By default, I think steam boiler was settled at 127º. Yes, it works fine at 125º but I do prefer the extra pressure as steam is not very dry on the Vesuvius. Recovery is faster too if temp is set a little higher. Anyway, I have this pressure interference with the coffee profile if I go up 120º or so, usually bad at 125º.
The Vesuvius pump pid is really sensitive and is very dependant, as if has to be, to coffee dose, grind size and puck prep. It has many options to fine tune this behaviour with pump acceleration and pid settings. Of course you have to learn how it works and set as you need but… This should be the same whether the steam boiler is on or off.
What I’m doing for years to deal with this nuisance is going to eco mode (easy with just four touches on the screen) not allowing to go above 115ª before pulling the shot. When shot starts there is no problem if temp ramps up to the 128º. But… shouldn’t be that way.