My tuner messaged me the other day stating another 3.5 EcoBoost he's tuning (head games ported heads, twin EFR's) does not have the same negative trim issues as my truck, and his port work and mod list is far more aggressive. I considered the fact that perhaps I'm getting lower than optimal fuel pressure at cruise and idle (where the LTFT's go the most negative) causing poor atomization, but the DI pump and injectors are brand new, and the truck exhibits no signs of drivability issues other than poor highway fuel economy. I also double checked that rockauto sent me the right O² sensors and they are...17323 and 17321 respectively.
I smoke checked the intake as well. Found a crack in my intercooler and patched it - however it didn't make any difference in my LTFT values once it was repaired.
I'm open to advice, as I'm nearing the point of throwing parts at it - perhaps another set of OE injectors.
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