There is a thumping noise that happens sporadically from the drivers side wheel

What is your question?

We think it has to do with idler or pitman arm. When we took it to a chevy dealer, they said they werent bad, but starting to wear. They had no idea about the noise. It happens mostly on hiway driving and seems to diminish when we let off the gas. It is a rapid "tat-a-tat" noise.