Boost responce is Lag which is different again (tho most people think boost threshold is lag).

As an example, most people say T4s are laggy on a cossie as they dont give you any power till 4500 on most engines, but in fact that just mean they got a high boost threshold.

T4s ARE laggy to some extent tho, as in even when you ARE well within the above explained boost threshold, you still got a small waiting time between when you boot it (WOT), and when the power comes. THATS Lag

Im lame at explaining stuff, but i think that makes sence