It looks like almost everyone here is not using the term "turbo lag" correctly. You must clarify if you are talking about boost threshold or turbo lag. They are different and often confused.
from Wiki: (
http://en.wikipedia.org/wiki/Turbo_lag)
"Lag is not to be confused with the boost threshold; however, many publications still make this basic mistake. The boost threshold of a turbo system describes the minimum turbo RPM at which the turbo is physically able to supply the requested boost level. Newer turbocharger and engine developments have caused boost thresholds to steadily decline to where day-to-day use feels perfectly natural. Putting your foot down at 1200 engine RPM and having no boost until 2000 engine RPM is an example of boost threshold and not lag."
To be clear:
Putting your foot down at 1000 rpm and waiting til XXXX rpm to get boost built is boost threshold.
Putting your foot down at 5000 rpm (or anywhere above boost threshold) and waiting X.X seconds for boost to build is turbo lag.