Let's look at one wire, the 'hot' wire of one outlet. This is a brand new piece of copper, it's nice and shiny. You may have cleaned it before inserting it into the Porter. It looks beautiful. There is a point where the wire is in contact with the receptacle. This is called an 'air tight seal'. There is no oxidization at that exact point. But what about right beside it?.
In your head, enlarge that point. Enlarge it to the point that you envision a Tesla Coil. Now imagine our electricity is 10,000 volts. What do you see?........ Lightning?...... tiny arcs?. Drop this down to 120V, and you simply get smaller arcs, but they're still there. They're immeasurable, but we can hear them.
At other forums, I've tried to introduce the concept of 'micro-arcing', and got laughed at.
The act of 'burning in' simply give the wire time to oxidize. Copper oxide does not conduct electricity. So, over time, this micro-arcing decreases.
Here we go: go to the hardware store, electrical section, and buy some electrical paste. It comes in a tiny tube. It's black and messy. And right now some of you are laughing. It's uggggglyyyyyyyy. Who in their right mind would install brand new dedicated lines, and then smear them with this crap?. Me!. That's experiment #1.
Let's look at brand new multistrand wired power cords. Is there micro-arcing between the actual strands in the wire?.
Experiment #2: you have Romex left over. You can get male receptacles at the same hardware store. You will need to order iec plugs. Build some power cords, remembering to smear the paste at all contact points.
Listen.