I read the sticky and did a search but haven`t seen this mentioned...
I have the headers here. They supply lengths of wire for extending the o2 sensor wires. I have been told that it is not good practice to just cut and extend the wires by a freind who works in the maintenance department of a dealership. Has anyone had a problem doing this?

 

Well, I did that, but some how I managed to melt the extensions to the header!!!

Now, I bought some GM Corvette REAR 02s (they are much longer) and they work great....

 

On my dad's Z28 we did the wire extensions (properly) and they still f'ed up on us and gave us an SES light. I decided to go with the regular O2 extensions on my car, and I haven't had a problem yet.