Only very few Amsoil oils carry the API certification (some synthetic blends and some newer oils) but Amsoil "thinks" all their oils pass or exceed the API certification. See Amsoil's explanation why their oils do not carry the API certification at
I believe API's website does list which company/oil has the certification (I seem to remember seeing it once before.)
I will look into finding some official NOACK numbers. If you can get the numbers, please let me know. It is rather dangerous to quote another (unofficial) website for numbers.
The Amsoil 15W-40 is a great oil.