2001 Silverado 2500 6.0L stock work truck

For a while now I've been noticing knock during hard acceleration. I was thinking my fuel pump was starting to get weak and since I've never changed it since I've owned the truck I went ahead and changed it. Of course the knock is still there so I get out the scanner and notice that it never goes in to open loop even with tps at 99%. What should I look for to remedy this issue. Anyone have any ideas? Thanks