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 bought the truck, I have been experiencing random symptoms like hard shifts, brake dragging, and short runs of mild vibration like rumble strips. This is all subtle but annoying. I ran a can of Seafoam through it without result. I always assumed that some of this was due to tires. I just had new tires installed but that didn't change anything. What are your thoughts? ODBC2 is not displaying any codes.