A "bad" turbo generally becomes a huge restriction in the exhaust AND intake paths effectively choking the engine. While it will produce non-turbo power, a lot of it is used just getting fresh air into and exhausting the hot gasses from the cylinders. It really comes down to the nature of the turbo failure, though.

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8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim