I know of two people who have suffered pulley problems at high rpm on the zetec engine.

The tensioner on the black top is automatic so I will be looking to change this for a manual adjustment one like on the Rover turbo engine or possibly another one if anyone has an alternative solution?

I would like to use metal pulleys as I've been told the plastic ones can fail too.

The plinth on the pulley is also 25mm diameter so I will be looking to make a wider one as Ive heard of the side load on the idler snapping the bolt off.

I would prefer to buy one off the shelf, before I look at making one up.