Personally... I think it takes track conditions to really get a motor to the " sweet " spot...

Many time i though i had the tune nailed in the pits and then pull my truck/bug of the track ethier faaaat or burning up...

I may just be a bad tunner though... Ive seen scott sternburg (sp?) still at his pit and rev his engine and teek the needles to what seems to be a perfect tune!