We installed the Standard coils last weekend but I haven't driven it much due to the 'stay at home' order. I don't believe the problem is solved but I'll report when I've driven it more. At this point, I've replaced plugs, coils and injectors and I ran a can of Seafoam through the tank.
I...
I wouldn't rule out valve seals. You may not always see the smoke, particularly if you're looking for it through your mirrors. It doesn't take much oil to create a puff of smoke and the seals could be in an early stage of failure.
I bought my 07 Limited last fall with 192k miles. It threw a P0308 code right away. Ford dealer told me it was #8 coil. They replaced that coil and all 8 plugs. The code returned almost immediately. A shade tree mechanic friend replaced 8 injectors and the code has not returned.
Since I...