motor D13 MP8. I have a leak in the exhaust leak

You have a leak in the leak?

Diesels dont smel like gasoline, EVER! If you have gasoline it wont run. An oil burn will smell like sesame seeds and have blue smoke.

How often are you checking the oil?
Is the turbo wet on the exhaust side?
An exhaust leak will have black soot at the point it is leaking.
To get the smell into the cab means the leak is in the engine compartment.
Check the EGR line would have been my first guess. The EGR if you have one will be a metal pipe the diameter of your thumb (usually). It goes usually from the exhaust manifold too your intake. DONOT remove this pipe. It has a nasty fine for EGR deletion. Again look for soot at the leak. (black charcoal)
Check the pipe and flex pipe under the cab.

 

So then it is a matter of checking the mechanics job. It sounds like the mechanic screwed up.
Take it back to where it was repaired and file a complaint. Get the job warrantied

 

Like a hole in the side of a black hole? Either matter gets out, or matter gets in the second hole and is no longer affected by the black hole