Bought a cheap Bluetooth ODB2 dongle, down loaded 'Torque' from android app store.
I wanted to check intercooler , boot and vacuum pressures.
This is just an observation...

I noticed on starting car from cold, vacuum read about -16.1 @ 1120rpm. then when engine settled -23.3 @ 920rpm tick over.

In my Mk5 Golf GTI vacuum was always -22 ish regardless from cold or warmed up.