My brother had one for a week or so on his first car (68 Cutlass w/ a 350). Car ran different every time he drove it. One day it ran great and the next time it bogged and farted. On the good days it made a lot more power then the Q-jet the car came with.

They are, or were, popular with the monster truck, mud bog, sand drag crowd. Idle to the line, floor it, and then idle back.