Turbo High Altitude Engine Flooding?

[Paul Sharp]

Here's some new info, FWIW: I can't find any "barometric controller" on my turbo model in the diagrams, etc.

But I did talk to the mechanics, who said that with Piper Aerostars, for example, this is a common attribute: at high altitudes the pilot needs to reduce the mixture somewhat until the turbos begin to spool up, and then add the rest of the mixture.