Wideband O2 install and use... tips?

Where can you get leaded fuel?
I have had my LMX-T wideband for some time now. I used it for many miles on my car each time transferring it to the new vehicle when it's ready...never cleaned anything.
I have found it difficult to lean an engine out at idle with a large cam though.l have jetted cruise to lo 15's but keep them a little rich now in mid to hi 13's...i just like a little more fuel to be on the safe side and wot around 12-12.5