had this same problem happen to me recently. had the copper pipe pressure tested and it was leaking at a weld. i think it was the inlet one to the turbo. the mechanic replaced it with a new one from nissan. cost about $150 aus for the pipe and two hours labor.
They asked a supplier about replacing it with a braided line but he said this particular one wouldnt work because of the shape and it would still need a pipe end on it or something. Dont know if this guy knew what he was talking about tho.