Right update time the customer picked the truck up yesterday. I could not find anything wrong with the bottom pulley but when scoping the crank/cam sensors and check against a known good one (My L200) I found a difference of about 5 degrees in cam phase so advised that the belt needs to be replaced urgently as it's now 4,000 miles and six months over due. I can't say for sure if this is the cause of the customers problems but I need to start at a known good starting point and a dodgy cam timing issue is bad news. I have given the customer a price for the belt and told him that if he drives the truck and the belt now snaps he only has himself to blame. Thanks for the help folks. If I get another look at this one and get a fix I will keep you posted.