I have bought a few knock-offs, as in a Blitz RFL BOV, which i have never had a prob with it in the 6 months it was on my car. and it only cost me 30 shipped, compared to that of 200+ shipping. I also bought that Voltage stabilizer, which i actually noticed a difference in acceleration, and a smoother idle and also in all the electronics in the car(lights were brighter, my sensors read more accurate, which in turn gave out better readings, which in turn allowed better engine management, ie. more power) I used it in combination with a earth grounding kit.