Cheers for that, I actually didnt bother as a) I know the Mercs arent laggy, my brother had one and 2) its an an automatic luxobarge, its hardly going to be developed for the sharpest response. I guessed he was probably referring to boost threshold.
Amusingly, theres a Clarkson clip that perfectly demonstrates the difference between lag and threshold, its amusing as he is trying to prove the exact opposite.
From about 1:20 here:
exactly the example I thought of when the lag chat started, he complains about the lag tut tut