Knocking whenever I let off the gas...

[DS900]

This started today, no strange sounds when I'm accelerating or braking, but as soon as I let off the gas I hear a distinct knock knock knocking sound from the engine.

When I got home today, I popped the hood and found this:

http://i.imgur.com/K1xzy.jpg

What could have caused this? What can I do to fix it?

Thanks guys

[ricerboy4g64]

i say new plugs and wires. you dont want carbon track since one of your plugs could be going bad.

[ricerboy4g64]

you should check to see if you have oil seeping threw your spark plug tube seals, basicly get a flash light and look down in there before you remove the spark plug if theres any oil you should get valve cover gaskets w/ spark plug tube seals.

[ni2]

This started happening to my gtz also. Most likely the other three tower seals are on there way also. If you have any lifter tick you may as well fix that too since you'll have both valve covers off.