Only time someone really asked for it. I was on the way home from work at night. Stopped at a light, no one around. Toyota Camry full of teenage guys pulls up next to me. After a second I realized, "They're revving the engine at me!" I could barely hear it over my exhaust at idle. Light turned green, and they "took off", well, as much as they could in that car. I just drove normally. Wasn't even worth it.
Then I was driving a road in the summer. Windows down. If it's above freezing, I will probably have my windows down, I just like it. Anyways, I'm in a right lane, going the speed limit. Then a lifted '90's Ford diesel matches my speed in the left lane. Then he mashes it and lays down a plume of smoke. I can barely see, and I'm coughing on the crap that he just belched out. I catch him at the next light, and I'm pissed. Light turns green, all he could do was keep even with my left rear quarter panel until I had to slow to make my turn. He didn't look too happy that his diesel rolling coal just got beat by an old gasser SUV. He probably didn't hear the whine of the Whipple, though. For the record, I didn't break the speed limit, but I sure got there in a hurry.
I swear, it might make more power in higher RPM's, but where this truck really catches people off-guard is from a standing start, with the low-RPM torque. People who ride with me definitely don't expect it, especially for something weighing 4600 lbs. It usually takes a second for the seatbelts to unlock after doing that though.