Why Do I still have a CEL after installing 02 Bung Extenders?

[prometheus036]

So like the question states, I have a reappearing CEL light that came back on after installing my test pipes. I took the 02 sensors out before breaking the bolts on either end, and did not use an impact until I was hitting the topmost flange bolt coming from header to cats. I put in the 90 degree bung extenders, and also threaded in the 2 inch extenders onto that to make sure I had plenty of room for the sensors to be out of the flow of exhaust gas. It (the CEL) keeps coming back, and I'm not sure why, as they are out of the direct flow of exhaust gas. Did I make a mistake by putting the extra extender on? Should I only use the 90 degree extenders? Thoughts and opinions are greatly appreciated!

The codes are P2098 and 2096, voltages are at 0.290 and 0.280, which seem normal.

Also, I have some buzzing coming from the trunk/hatch area, around 3-4k rpms, is this normal? I've heard it comes with the territory of having RTPs and Resonated Axle Backs.