yes you can clean it yourself, I am sure there is a post on here on how to do it, remove the electrical connector then the four bolts and clean with some carb cleaner.

Does this earth strap really work? Is there a picture of where you attach it to on the engine? I supppose I can't see the lift eye becuase of the airbox?

in theory supposedly although probably better moreso for the electrics than any great noticeable difference on tickover. My car fires up everyday without fail and ticks over super smooth.

The earth strap didn't do anything for me unfortunately