Don't know about the 13.8 being the best for peak power , but the order you have the AFR listed is correct .Originally Posted by 2002_z28_six_speed
13.8 just seems way to lean (unless you mean before power enrichment) , 12.5 to 13.2 is about right for Naturally Aspirated engine (Power Enrichment state) .
With a COS3-5 you can command a power enrichment like state in {B3647} and not need PE , or you can remain Stoich and let PE come in as normal and set it to 12.5 - 13.2 range .