If you run an 02 sim, and dont replace that specific section of exhaust, what do you do with the bung from the sensor?

 

Are you talking about on a stock or stock style setup. Why are you deleteing the rear O2 sensors?

You can either cut off the wires on the O2 sensors and leave the actual sensor in there or you can put a plug in there.

Summit sells O2 sensor plugs or i'm sure a hardware store would have something that will work.

http://store.summitracing.com/egnsea...nresults=false

 

I heard of someone threading spark plugs in there as a temporary fix which became a permanent fix.

 

The threads are M18x1.5. Just get a hex head plug and screw it in.

http://store.summitracing.com/partde...part=ngk-91301

 

For my Mufflex Y-Pipe, which had hook ups for the 3rd and 4th o2 sensors (my car only has 2 o2 sensors) I threaded in some big tractor-like spark plugs since the designated bung plugs that O'Reilys had wouldn't fit in there since the bungs were "off-sizes."