I have spark knock under a load in my engine. GM has a bulliten out for this where you replace the rear knock sensor for corroison on the sensor. I have replaced the rear knock sensor, performed an fuel system cleaning, updated intake gaskets, new plugs and wires,and am going to try to get it reprogrammed this weekend. Now I did not replace the intake gaskets, or the plugs and wires for this concern.I replaced the plugs and wires cause it has a 140,000 on them, and the intake gaskets were replaced because I had the updated ones from another job. I was going to replace the fuel filter tommorow because it may cause this and it needs replaced. any help would be great, thanks.

sounds like a timing issue. Try a different octane?

yes I have tried both 87 and 89. with no difference ecept better mileage with 87. Im going to try and get it reprogrammed this weekend if I get a chance. I was going to by a bottle of octane booster and add that to see if it helps.