mine runs fine at 14.5:1 afr, about 0.5%, abit lumpy. runs alot smoother at 2%.
thats with 500bhp engine on 8 greens.

if spent abit of time wen mappin can get the co right down. and run smooth

the mixture screw is only for idle, as wont even notice the diff at top end, thats all done to map, and fuel pressure its been mapped at.