hmmmm......well, at 45,000 km any "new engine smell" is most likely gone.
I reckon the burnt smell is coming from a part of the exhaust system pushing against something, and burning it, when the engine is "torqued" over against the engine mounts.
I’d start by looking for anything that could burn which is near a part of the exhaust. Maybe a harness strap gave way, allowing a piece to come in contact with the manifold (header) or overpipe.
Back in the day, if we had someone we didn’t like, we would lay a piece of limburger cheese on a cool exhaust manifold of his car …….. let that sucker figure out why his car stunk, after he fired it up…….
humfrz