Need help chasing down knock

Info on my setup - 1995 K1500 151000 miles, 3.73 gears, 4L60E. 350 with Hedman long tube headers, 2.25 dual exhaust, O2 sensor is in header collector. Has 14 psi at the injectors, Delco EP381 fuel pump, fresh cap/rotor, Davis Ignition coil. Timing is set to 1 degree advanced, I really should check if the balancer has slipped. Using an AutoProm and TunerPro for tuning. PCM is a 7427, $0D BJYL stock.

I've been seeing some KR while tuning, see the datalog I've attached, it's a pretty long drive. Somewhere around 2-4 degrees that would kick in fast, then taper off. It's in the 60 and higher KPA range for the most part. This datalog was taken with EGR, DFCO, PE, and AIR disabled. The BLM tables look pretty good to my rookie eyes, and the main spark table is stock.

I pulled a couple plugs tonight to get a better idea of what's going on, and I found this. These plugs have been in the truck for a while, about 8000 miles. I'm not an expert plug reader, but it doesn't take an expert to tell that these are bad. Clearly not a case of false knock I'm chasing here. Any advice would be much appreciated. Looks lean to me, but why when my fueling tables look nice?

http://i1187.photobucket.com/albums/...psr8iozaxi.jpg

More pertinent info - I've only been tuning for around 1000 miles, so who knows what conditions those plugs were running under for the previous 7000. I think I'll grab a new set of colder CR42TS so I can get a better picture of how it's running, and check if my balancer marks are accurate.