In my quest to fix my floating idle issues, I finally decided to check codes vs. continue to replace parts. To my surprise I did pull codes even thought my CEL wasn't on. Here's what I found: Key on engine off- Code 67 and Code 66 in continuous memory (VAF/Mass air flow sensor fault, below minimum voltage). So I got 67, 10, 66. Key on engine running- Code 41 (HEGO HO2S sensor voltage low/system lean) and Code 91 (which is the same as Code 41) Code 41 and 91 is odd since I recently (within 300 miles) replaced both O2's with motorcraft sensors. That was the first thing I did to address my floating idle issue. I also should note I am not running cats. When I did, I still had idle problems so nothing changed. Where should I go from here??