From what I've heard and gathered from driving 4:10s, they really do rocket you off the line. The shifts seem to be a lot harder too, but maybe its my imagination. It will really wake up your car, and most likely youll have to adjust your whole driving style. My friend tells me though that when he gets farther down the track they seem to kinda hold him back and the shifts lag a little bit. Like the engine is starting to get out of the power band too much before his car shifts. Who knows though, it might just be his car?