I am with icarp. If you are seeing 14 at 4000 you will be much leaner above that and with S cams peak power if going to be around 6K plus. At that point you are probably so lean that you will burn things up. Lamda or leaner is only relevant for low load and light cruise. Chart below gives general mixtures to shoot for.
Your 11 to 12 between 2500 to 3500 is not a problem, your 14 at 4K is. You should probably shoot for 12 to 1 thru the entire rev range.
From the Performance oriented site, the 3.2 is closest to your configuration.
There is some good tuning information on how to correct the A/F mixture at different points here as well, link below.
Performance Oriented
Hope this helps,
john