Thanks for those suggestions .... now the T4 check has eliminated a set of possibilities I'll be running through some different checks ... Although I checked for obvious leaks 'upstream' of the engine I haven't looked further as my previous experiences with leaky intercooler/feed pipes was that it gave plenty of smoke but it was sooty and black (my smoke is blue and light coloured) .... if intake leaks can cause blue smoke I'll certainly recheck all of that more thoroughly. .... I certainly don't claim in depth knowledge of modern diesels
Cheers
K
K