hey , i have a b16a in a ef9 , i just did a header swap , my OEM header has 2 o2 sensors , on skinny one and one fat 1 , My Dc 4-2-1 header only has 1 o2 sensor insert , wha shud i do , wich 1 shud i put in to the dc header , the skinny 1 or the fat 1 and shud i run both or just 1 ? some plzz let me kno asap

 

Thats because you got a OBD 1 header but your car is OBD 0, no big deal though. One option (other than converting to OBD1) is to have another o2 bung welded in place where the OEM one would go and this is actually the proper way to run it for safety inspection reasons in most states. Another option is to just not run the secondary o2 and use ypur main one in the provided o2 hole, I have heard it will not set a check engine light but I have not done this so I am not really recommending it, just letting you know what I have heard

Of course the obvious answer would really be to get the right header with 2 o2 bungs in the first place....but I assume your not doing that

 

Put 2 bugs in the appropriate location at the merge point like the OE header. Contiue to run both O2 sensors.

should

 

convert to obd1....... or just weld a bung