It will improve performance, difficult to say by how much. Usually 3-5 bhp is about average for a good induction kit. I have the BMC CDA fitted to my HGT and it sounds great. It was already on when I bought the car. I'm not totally convinced I would have bought one if it wasn't fitted though.
i know but at least i know that the BMC ones work!!! the only difference is that its not carbon, rather sprend a bit more on something that might help my hgt go a bit quicker!