If the knock sensor replacement doesn't cure the problem. Try replacing the power stage. I had replaced the power stage in my 745t because of a no start problem. The car started fine, after replacement, but continued to run bad. Replaced almost everthing. Finally took it to a Volvo tech. He found that the new power stage was bad. He put in a another new one, and the problem was solved. He said he had never seen a power stage cause the problems I was having. Usually they either work or don't. But after my experience, it appears that sometimes a bad power stage will cause weird timing problems.
Brad