I asked my mechanic abut the cause, it seems that it is quite possibly related to the head replacement done a year ago when I first got the vehicle, but it's hard to be certain.
Quoting my mechanic:
to answer your question as to why this happened it could be caused by an error in assembly possibly bending the valve during installation or while putting the engine back together if the timing belt was not installed correctly the first time and bent the valve but both of these you would have noticed when driving there would have been a poofing sound from the exhaust but it could explain the turbo power problem you were telling me about, there would also be smoke coming from the tail pipe usually light grey in colour from incomplete combustion, possibly an old head that hasn't been used for some time and the valve siezed in the guide causing the breakage, but I have seen them just do it out of weakness although never in a low revving diesel
As for who I am using for repairs... kidwrecked pm'd me his brother's info, This is NOT a normal garage, but a very professional sounding hobbyist who seems to absolutely LOVE this sort of work, he has all the right tools and such, and he sounds like he really knows his stuff, but he has limited time to work on these as he has a full time job as well, his shop rate is dirt cheap, but the trade-off is the time required for the work, he has so far only put in 4 hours of work on the vehicle, but it has taken well over a week to do that. the introduction I was given was as follows:
kidwrecked wrote:The only help that I can give is that my brother lives in Strathmore. He is a machinist and a VERY competant mechanic who likes to diagnose and FIX the problems rather than just replace pieces. He is very familiar with diesels, as he worked for a Kabota tractor dealer for 10 years out here before moving to the flat lands. He thrives on Japanese vehicles and has extensive experience with modifications, turbos, diesels, rotary engines, right hand drives, etc. He has a small shop and little time but I know that he would love to diagnose your problems and help. He is completely honest and trustworthy
So far I am very impressed, he sounds like he really knows what he's doing and really enjoys this sort of thing, he has sent me pictures at every step to show exactly what is wrong with full explanations as to what I should be seeing vs the way things are, this is not someone who is just drumming up extra work that isn't really required, he doesn't charge a lot per hour, and judging by the progress so far, and the hours he has spent, he doesn't seem to be wasting any time.
I doubt he has time to work on every little thing, but he certainly seems to be able to handle things well. Once we're all done, and presuming that I'm still as happy with his work as I am now, I will ask him how much Delica work he wants to do, and let people on here know.
I read the whole thing and all I have to say is I'm really sorry. The guys in Pro-Active are expensive but they've done this before; you can always take the van there and ask them for an estimate. However it seems that you've found a new mechanic in the area and this is good news. When you have a chance, please share the details with the rest of the Calgary owners. 
