i fitted them a while back at a garage,there ok if you are doing the millage,work well with modern eng man you can set them up via a laptop as you have to fool the cars management for switching it on ie injectors,o2 sensors,you then splice in to the vehicles looms etc
various different ways with the fuel tanks aswell ie split tanks or fit them in your spare wheel well and so on
they say theres about a 5% power loss on gas tho.