Mate Had a kook at you log , unless you have hacked away at the "Knock Control Advance Max A" table you have -1.5 to -2.0 knock correction happening between 6400-6700 that's the chunk out of your kc learned
http://www.datazap.me/u/hsayaovong/9...1274&mark=1040
you say you have been adjusting Base Timing A and Base Timing B. As far as i know Base timing A is for limp home mode or AVCS fail and not generally used.
You might want to read this post , i'm not guaranteeing its 100% correct but I think I should give you some more useful info
http://www.ft86club.com/forums/showthread.php?t=61820
It might be worth considering an E-tune from the OFT boys (since you already have OFT) its $200 and they will explain the changes they make. You will still learn and it will be safe, lots cheaper than than a damaged engine.
I am actually considering this option myself.