4% at tickover ?sounds fine. the co screw only controls the co at tickover, once the engine is revved then the chip takes over, if your engine is running lean at top end then its a chip problem , you need to talk to stu (motorsport developments) , some dyno "experts" who say a chip is running lean at top end dont have a clue as to how the management is set up, other times it could be that your running more boost than the chip is set for (but 22psi isnt a lot for stage3 and greens) cheers nomad