That would be this, I reckon.
This "when scying TB" was probably supposed to have been "when synching the throttle bodies", I guess.
To the first question: whether the engine is warm or not has absolutely no effect on the TPS Voltage.
What is really important, as detailed in the thread linked above, is that there is nothing interfering with the throttle body closing completely. Connecting rod disconnected, high idle mechanism disconnected, throttle stop screw all the way out. All that.
What makes it difficult to land exactly on the 157 mV is that the business moves a bit when you tighten up the screws. A couple of attempts will show in which direction and how much (approximately) it will move, allowing a better guess at what it should be before tightening. Also, within 2 or 3 mV is close enough, actually.
When synching: the bleed screws are, more or less, only relevant at and just off idle.
Based on the procedure outline from page 572 onwards in this workshop manual
https://guzzitek.org/gb/ma_us_uk/1100/V11_1999-2003_Atelier(Compil-GB-D-NL).pdf
The procedure there is for using the Guzzi diagnosis tool. We're not, so ignore the bit about 3.8°. Disconnect everything from the throttle bodies, and measure the Voltage with the multimeter.
Re-connect all the linkages.
Close the bleed screws all the way.
Using the tool of your choice (vacuum gauges, or whatever) balance the throttle bodies at about 3,000 r.p.m. .
Use the bleed screws and said tool of your choice to set the idle speed and balance the throttle bodies at idle.
That's a summary. Read the thread in the link above for the full story.