Originally Posted by qweesy
... and better drive-ability
^^this is the biggest benefit. Tom's tune removes the bog you get on take-off, so that launches, even non-aggressive ones, become easier. The idle is less erratic, the rpms don't jump so high on start-up, the rev hang between shifts is minimized, and you seem to get more torque in the low rpm ranges. And the tune allows you to completely disable traction control, if you have it.
Mine: 2008 Saab 9-3 Aero SportCombi XWD: 82k, Black, MANUAL
Gone: 2002 SVT, #1654
Hers: 2010 Focus SES: 70k, Ebony, Auto, Moon and Tune