My gas gauge drops to E sometimes. I love when it reads empty as I'm pulling out of the gas station after filling the tank. I had it scanned and I'm being told its the sending unit. I am looking for a replacement part and I am getting two different results. I believe my truck was built in December 2006. (I have a 2007 XLT Screw). I think I found the right one, PS-353 but on Rockauto it says its for it's for FLEX fuel. Is there a difference between the FLEX and non flex engines? My wheelbase is 138.5". I also noticed that some parts say they are from 12/3/07 so I'm guessing they changed the style of pump/sending unit too.