I had my over run valve replaced a couple of months ago, any idea what it is and what it does?

It's a cutoff valve; it's to reduce the fuel going into the engine when it isnt needed - primarily when decelerating or coasting. I *think* it shoves air to the pipe instead, but that's where my knowledge dwindles I'm afraid.

Usually made of plastic, hence they wear down and need replacing sometimes. You can actually get metal ones which don't wear, but pretty expensive.

cool thanks!

No problem.