Awesome. I noticed the sound flag AIF_HEARDLOUDNOISE gets turned on whenever the player moves inside the enemys loud noise radius which seems to always be set to there sight radius meaning they always go after the player when in sight. It makes me think that since the original game had a walking mode for the player that that was also a stealth concept in the game I never noticed. Makes me want to pop the original back in and just see if that's true. (edit: played the n64 version and walking does indeed prevent loud noise.)
These are the ones I know of (named from the debugai screen):
EnumAIFlags
AIF_ATTACKING = (1 << 0), //Already defined
AIF_WASSOLID = (1 << 1), //Already defined
AIF_FIRSTATTACK = (1 << 2),
AIF_HEARDLOUDNOISE = (1 << 3),
AIF_BLOWNAWAY = (1 << 4), //Already defined
AIF_GOBACKTOLEASH = (1 << 5),
AIF_RESURRECT = (1 << 6),
AIF_REGENDELAY = (1 << 8),
AIF_SEETARGET = (1 << 9),
AIF_NOCHASE = (1 << 10), //Already defined
AIF_REGENERATEANIM = (1 << 11),
AIF_NOTHINK = (1 << 12), //Already defined
AIF_RUNNING = (1 << 13), //Already defined
AIF_GETATTENTION = (1 << 14),
AIF_REGENDELAY2 = (1 << 15), //not really sure what this is
AIF_HEARDQUIETNOISE = (1 << 16),
AIF_AWAYFROMLEASH = (1 << 17),
AIF_TELEPORTAWAY = (1 << 18),
AIF_TELEPORTMOVESLOW = (1 << 19),
AIF_TELEPORTING = (1 << 20), //Already defined
AIF_WAITFORCYCLE = (1 << 22),
AIF_DAMAGEPANIC = (1 << 23)
I'm missing 7, 21 and I'm not sure what 15 is but I think it has something to do when an enemy regens.