First, This isn't your average "Fuel Cap Light" thread so please don't write this off... Second, I keep good records of my fuel consumption. I do this via ultraguage as well as hand calculations at the pump. I've used the ultraguage for almost 10k miles now. Third, I believe this anomaly is...

Ok here is my issue my 2005 3.5L is throwing a P0171 (System Too Lean Bank 1) and a P0455 (Evaporative Emissions System Leak (Large Leak)). I thought it could be my evap solenoid so I took it off and cleaned it and cleared the codes. Since then, about two weeks now, the P0455 has stayed off but...