Here are the results. I'm putting in a nitrous kit, so I pulled them to switch to a colder heat range plug and this is what I found. They are wet because I soaked them with PB Blaster before attempting to remove them. None of them stuck or were unreasonably hard to remove.

 

wow that is nasty!!!!

 

What causes that?

 

Using poor quality gas. your valves look just as bad. Eventually these deposits will increase the octane requirement of your engine due to hot spots and lower flow and thus performance.

Those are fuel deposits, plain and simple.

 

Yikes! What gas do you use (grade and brand) and do you run a tune?

 

Okay, okay. I ONLY use Shell V-Power and run a 93 tune from Brenspeed. This past winter I switched to the 87 tune to save a bit at the pump, but still only using Top tier gas. I believe the pictures are misleading, because the carbon I did have on the plugs was wet with PB Blaster and it looks a lot worse than it was. I let them soak for a few hours and all of the residue wiped right off.

 

If you look at the electrode, it is relatively clean like his valves should be. That has to be PB Blaster because the electrode didnt get soaked with it.