I am an Ally as mine was replaced. But be advised that the idle could be several things. Leaky intake manifold gasket; Leaky ICV gasket; Leaky PCV Plate that can cause the rough Idle. Those are all manageable repairs from a cost standpoint. And a lot of folks here have done those repairs themselves. Mine has 174k on it and the PO had the engine replaced at 92 during all the Nikky hype. I just recently replaced the intake manifold gasket and PCV Plate Gaskets due to rough idle and check engine codes pointing to O2 sensors.
It runs perfectly now - I love my 5er. -= JT