I'm not even sure what the knock values are for a stock motor, but I have the same situation. My knock sensor reads low (good) at idle, but it reads around 3/4 of a full bar on the PFC commander under both cruise and WOT. It never exceeds this 3/4. I'm also running very rich (low 8's under load, as I've only had time to tune idle and cruise so far).
From what I've been reading, every motor is a little reads a little different (especially modified) and with the stock sensor you have to 'learn' what is a safe reading and what isn't. I don't know what the truth to this is though.
To solve your problem, so you don't have to rely on tuning with the stock sensor, rent/borrow/buy a 'knock box'. Then you can tune without worry, and also find out what is normal for your sensor.
http://www.theknockbox.cc/content/view/5/5/