O2 dummy sensor
 

I just recently put headers on my 1990 full size blazer, but now my 02 sensor is just dangling! Is there a dummy sensor or should I tap a bung right behind the header? Any thoughts or suggestions would be appreciated!

You need to install the O2 sensor for your engine to run correctly. It is used for fuel management.

Put a bung in the collector, if you dont have one convert it over to a heated o2 since you moved it further from the engine.