Originally Posted by Can't Know

Boy, I sure would. The things get old and close to out of range and will trigger codes but often not a CEL. Bosch says to test or replace them at 100K so you're well beyond that and you're likely to see an improvement in economy and maybe performance. If you wait to the CEL they are basically not functioning at all. It may be pretty tight, if you can't break it loose try getting the car hot and then see if it will start to loosen. If so just get it loose a turn and let the car cool down before you remove and replace it. If it's still very tight after you get it hot then let it cool and try again in five-minute increments. The different rates at which the parts cool can help to get it loose.