Has anyone done this on the 5.4 and to what success?

I bought my truck with 100k miles on it and the oil seems tostart getting dark around 2k mi. I'm using Penzoil withthe recommended 5W-20.

 

This is normal. It's getting dark because the oil is doing its job. Picking up and suspending ingested contaminates and combustion by-products. The higher the mileage, the sooner the oil will start turning dark. This is due to component wear (rings and such). The detergents in the oil are not for cleaning the engine but for suspending the contaminates so that they will flush out when the oil is drained. The newer the engine, the longer it takes for the oil to darken, but it will darken as all engines have blow by. This is why the PCV system exists on an engine.