Thanks Daniel, I am not sure what stage I am on, but I can tell you what I have done: vectra c intake, K&N pannel filter, de-restricted air box, 2.25" cat-back with Xforce muffler, remaped, the Australian version of the Astra G 2.2L convertibles didn't come with the pre-cat, I am getting a new header (4-2-1) and 200 cell magnaflow sports cat done next week. I am now looking for the 2.4 inlet manifold, hope it gives a bit more power.