What I have found to work best when using leaded gas is to NOT use a new sensor! Sounds screwie right, but a used sensor seems to last longer when using leaded gasoline. I take a good new one and run them for about 10 hours only on unleaded. Then after that make them for use with leaded fuel. While not the end all be all, it does seem to make them last with a fair reading for about twice as long for some reason. While I do not know why it, has proven itself time and time again, for the past 25 years of doing it.
So take it for what it's worth.