Im trying to replace my oxygen sensor, and I found that somebody has (at least) removed it in the past. They to tally screwed it up for me.
The nuts to remove it were all tore up. Every point on the nuts were tore off, and they of course didnt bother replacing them after destroying them.
I managed to get an 11mm wrench on one, and got it off, but I cant get the other one off.

I've tried using 12mm 6point, 12point, 11mm 12point, and a pair of those self adjusting pliars to get it off, and it wont budge.

What should I do?

 

You need a torch to heat them up and some vice grips, works every time!

 

Vice grips.

 

go to your local sears store and get this, they work like a charm. snap on also makes a set, but...they wont replace them if they break.

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

 

You can also try to split the nut with a dremel tool and a cutter wheel if you have one.
I am sure one of the other methods will work as well.

These things do work well too (as was mentioned):