I have a 2010 Ford Taurus Sho that the number 2 cylinder misfires under boost. We have replaced:
PCV breather assembly, PCV valve and heater, all six spark plugs, Cylinder 2 twice, all six coils, all six injectors.
Cylinder two is showing 12 to 15% less compression than the rest, vehicle does not misfire at idle but misfires under boost on cylinder2.
Any ideas where I should look next?
Welcome! I would scope the back of the intake valves to see if there is perhaps a noticeable difference in carbon buildup there. If there is, that is possibly a culprit.
If not, I would suspect the beginning of compromised piston rings. What engine oil have you been using (brand, weight) and for how long (miles/engine hours)? You may want to consider using Auto-Rx or similar treatment to see if compression can be restored. Fingers crossed.