2000 Chevy Silverado knock sensors

This engine has 2 knock sensors and they are located under the intake manifold and the manifold has to be removed to replace them.

There is a TSB published on this problem with this engine. It has to do with water getting into the hole where the sensor is installed. The cure they came up with is to use black silicone and build a dam around the hole with an opening in the back.
Here is a picture of it.