I asked that same question while at the service center with my GS350. Power mode changes the shift pattern and can hold a gear longer for best performance, it’s transmission software. It may drop your MPG a little bit.

 

Changes the shift points in the trans, holds the gears a bit longer. Since our cars have an electronic throttle it improves throttle response. Doesnt really ADD power.

I dont know what its like in a 250 but in a 350 you do get whiplash if you leave it on in stop n go traffic. It was also a bit dangerous when i would try for a open space. I had to take 2 tylenol when i got home Never again... Since i havent reset my ECU and i drive pretty conservativly 70% of the time, to me its like night and day.

 

Woooo, good information. That's good because I've always notice in regular driving mode, the lower gears shift pretty fast. Probably for better fuel consumption.

I'm definitely going to play with this tomorrow morning. I need an exhaust system so bad. Car's too quiet.