Originally Posted by Rusty

When you removed the old pipes. Did you use an air impact on any of the bolts? If you did. Did you remove the O2 sensors before or after using the air impact? The virbrations from an air impact is known to kill the O2 senors.
The other thing that it could be is one of the extension wires for the O2 senors has a bad connection when you spliced them in to the O2 sensor wiring.