Eric, not really finiding them. The 5.3l v8 has the sensors under the intake manifold. Is it possible that the 4.8 L has them as well under the intake manifold.
the knock sensor is screwed into the backside of the engine block, you should have 2 of them, 1 in each cylinder bank. they're probably a bit hard to get to, but they're there and are cicrular in shape with a single connector wire to them.
