I'm thinking about adding a tune-up box (don't know what else to call them, those electronic box of tricks that alter the ECU) to my 307 DTurbo (110 bhp HDi engine), and I was wondering if anyone had any experiences with them. There seem to be two models which fit the bill; Van Aaken and Tunit. Both around the same price and offering about the same increase in bhp & torque. Does anyone have any experience with either, and which is better?