Hi! I have a Astra sportshatch 1.8SRi and have a K&N 57i fitted and am looking at maybe getting anbackbox but I'm not sure. Eventually I want to get it hipped/remapped at regal using the eds technology! What gains can I expect just with the induction kit...also how much better would it be of I got the irmscher back box as well. Cheers! Ryan.