the last time i was a heavy PT user was 5.1....
at that time, apple click on the "vol" bar in the mixer window would calculate delay (in samples) of whatever was going on, on the track. i was always told that it wasn't a set number displayed, it was an actual calculation.
i just remember that the waves plug-ins were the worst offenders of latency. every thing would be maybe 100 samples off, drop a waves plug and now your 15k samples off.