if using Cipher for logging it won't let you select knock strength, you need to open Rom Editor and use the logging tool in there.
See my graphs for example, i got timing vs fly hp and o2 vs fly hp
you'll notice, o2 is more linear, from 4k to redline it just drops slighty but it does not jump as much as yours does, timing is higher as well, it does dip, but i guess that's just where the sweet spot of these engines is
http://s29.postimg.org/5ykcymuif/o2_hp.jpg
http://s1.postimg.org/c0kbimkcf/ign_hp.jpg
edit:
that's before i went for boost, obviously timing and o2 are looking much different now