When acellerating anything more than 10-15% throttle, the computer decides to retard timing because of knock. When over 50% throttle, its 6-10° of timing being pulled! Any idea on why this might be happening?

This is for normal driving around town....

I have the LT4 Km and have replaced damn near every sensor on the car... Would a bad knock sensor do this? What else could it be? Mods in sig...

BTW it's a pretty much stock tune. Timing has not been advanced at all..