i have a b16a and it has 2 o2 sensors if i am not mistaken, is there any way to use a b series header where the o2 sensor is by the catalytic converter and just reroute one of them? any suggestions would be great!!!

 

If your ECU needs both, the physical location of them matters less than their location in relation to the cat.
primary - before the cat
secondary - after the cat

 

so if i buy headers that have a hole for an O2 sensor where what would be considered the downpipe, but non where they are on the stock mani, how would i reroute them down? would i have one go into my cat, and then one in the hole on the header...? plus after that how would i extend them to get down there?