Nice tip BUT I wouldn't think it should do a thing for horsepower. Horsepower is a measurement based on how much 'work' the engine can produce, a measurement of power. The only way I could think that a replaced ground connection could induce more power would be if the ECU was hosed in some fashion. If that was the case then I would think anyone would notice some more bizarre kinda behavior from the ECU, like warning lights coming on, weird intermittent engine "issues", etc.