I've got 38,000 miles on my car and had been meaning to change the original oxygen sensor for a year or two. The lambda system was running open loop and super rich when I acquired the car. The culprit was simply a backed out relay pin, but this wouldn't have been kind to the O2 sensor. Once the lambda system was up and running it was very hard to dial in the mixture.
Past removal attempts with various solvents have been fruitless. Today I got out the torch, heated it up and after about 20 minutes "got it loose," except it was so seized it took the crossover pipe threads with it. I now have a gaping hole where my sensor used to be.
Knowing there were used crossover pipes floating around I figured I could just replace it on the cheap. Well, attempts at removing the cat nuts yielded the same result. It makes sense that one seized nut will typically mean all surrounding nuts and bolts exposed to the same elements will meet the same fate.
I'm fairly certain my exhaust system will not be removed without casualties elsewhere even with the usual precautions.
It might be time for an upgrade.