Is it normal for trailing plugs to foul worse that leading plugs?
 

I changed the plugs (9's) after 9k. I noticed that the leading plugs were in much better shape than the trailing plugs. It looked as if i put 3k more miles on the trailings. Any idea why?

generally when i pull plugs they have even carbon build up, are you primixing and what are your driving habits with the car? it could be due to a lot of reasons, do you have pics of the plugs? also what is the age and condition of your coils?

It's normal for the trailing plugs to be darker then the leading since its a smaller hole.

thewird