Interesting case of rubber rot, I've only lost one, the elbow next to the cruise control. I'd check out the vacumn lines, get a vacumn tester, their about $50 for an all metal unit, $30 for the plastic ones. I replaced my 02 with a Walker unit about 2 years ago for $100. Still going strong. Don't over look the stuff that give a false code like a loose ground or short, the O2 is just an electrical sensor and that signal can be corrupted even though the 02 is OK.
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Professionals have thumbs too.