Edit: it was my turbo, this thread can be deleted

 

The turbo seal might be leaking and if that wasn't included in the build then it's over to you. If they find it's their fault then they fix it? Wouldn't that be right? Was there a warranty on any of their work and do you clearly understand what they are responsible for? They should refund the diagnost money you payed if they if they find it's their fault too so bare with it if they are an honest shop.

If it was me I would had done my own leak down test before it went to them just to see if I could find it, I would also have pull the IC pipes to see if was any oil in them