Everyone has missed the other way to tell..
There should also be a boost gauge in the centre console if i'm correct..
It should have a -7 0 +7 measurement on it.. +7 being about 13.6PSI as it's in x100 something something's.. can't rememeber
anyways.. have a bit of a read up on how turbo's work..
for a turbo to produces positive boost it has to spin up to 40,000+ rpm which is done by the exhaust gases of the car..
once it's spooled up (can take a bit of time, that's called LAG) it'll start producing positive boost.. that's when the needle goes over 0..
at higher RPM exhaust gasses flow @ a higher volume & therefore car will come on boost much quicker..
@ low RPM it takes time to spool up.. accelerate in 3rd from about 1000rpm and watch how long it takes to spool up..
enjoy..