I also have the burnt plastic/electrical smell....I think my aux pump might have died. It smokes from under the intakes when I stop after a long trip (1hr plus). I am going to BMW to see if it ever had the recall done. It almost has 60,000miles (93,000km) so I am not sure what recalls they still honour.
if it's a federal mandated recall it should still be honoured.
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X5M, Eisenmann exhaust, 22" HRE wheels, catless down pipes, Stage II tune/X5 Diesel, Lowered & Tuned