Had anyone noticed if we are talking about a f4r turbo or a dci ?
if a dci , it actually states on the turbo replacement instructions to replace oil feed and return lines / clear out intercooler and pipe work.
I've done allot of dci. Engine changes now and it still takes me 8/9 hours to do everything properly ( not bodge any old bolt in any place o leave a few out )
10/12hours is optimistic on an f4r I'd suspect being more crammed in the bay.
Im betting the return has been restricted and kill the turbo, done more damage to the engine from it