2001 Dodge Ram 2001 Dodge Ram Pinging

Hello, So just like the title says. I have a 2001 Dodge ram that pings under a load or while while climbing a hill at highway speed. It idles fine but has a small miss. I all ready replaced my plenum gasket which I all ready know is a common issue with these trucks. It doesn't start pinging until the truck has warmed up. I just did a tune up on it as well. New plugs, wires and cap. I run 87 octane in it. Somebody told me it could be how my plug wires are ran. Why would this cause this and wouldn't it cause more than just a ping at loads? I can't seem to figure this thing out and I don't want to just start throwing parts at it. Can you give me some ideas where to look next. Oh by the way I did have a code pop up twice and go away for the rear o2 sensor. Could this cause this. The truck has power from a stand still but it seems like its gutless at high end. I don't know if this is normal for a 5.2L because this is the first Dodge I've ever owned and I have had this problem since I bought it. Please help.