I pulled 272/303 a few weeks ago with no air box & the car was running real lean (See Graph), I since put my air box back on "as needed for my Ram air hood" & put on me much needed Pro-M Optimizer for adjusting my air/fuel ratio issues & pulled a 279/317 consistantly. I'm going to be pulling about 10 horses more than dynoed though because they had to leave my air/fuel ratio a bit rich with the Ram Air once I get going, so basicaly one could comfortably say I will be pulling 290/325 or so, Enjoy.