I just read another forum question about headers and got me thinking about my own install. mine was the same dresser dual V&H headers. I wanted to ask is there a front and back 02 sensors? I dont think I paid attention to that when I installed mine. I just put the 2 sensors in the holes and never noticed if there where supposed to be one to each hole? Meaning I just had 2 sensors and put one in each hole? Is that wrong? Or does it even matter.