Hi megatexture..Nissan have told me that as well its a common issue, theres a reason why it happens and thats where the conversation with them finishes, i was told its a heat issue which means to much fuel,and thats what im trying to solve,this is my second time its had to be machined in 100000k,u cant keep doing that.ill be posting more info as i get it. Cheers thanks for u reply