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Take the cam cover off and see if the timing chain is still tight and look at the condition of the followers and cams.
Could also be EGR valve stuck open.
And could be a massive air leak from the throttle body or inlet manifold.
Also could be blocked or dislodged pre cat.
Have a look at these bits and see what you can find.
There are many threads on all of these problems so have a good look around the site and use the search box at the top right corner.