Swishing sound with heavy smoke?

[Duffsaw]

Hi All. 

I've a 2012 Forester 2.0D, with 260k kilometres on the clock. 

It's been trouble free I have to say. But over the last couple of weeks, I've noticed a change in her sound, a rough swish maybe, and the black smoke is very strong now. Almost painting herself black at the back bumper. I've had the intercooler checked, and no leaks or cracks. Any ideas??

[Nimpy]

Have you checked all the boost pipes?