Yup, can be engine bay also. I once had leaking exhaust manifold and everytime high revs can smell as the exhaust leaks more at high revLeaking exhaust can either in originate from engine bay or at under carriadge. Or both.
Change the manifold gasket dy....Engine bay exhaust leak can be quite serious...because the air vents, (to the car interior) is nearby.
Better get the problem fixed. Carbon monoxide from exhaust is odourless......but highly dangerous if inhaled for too long, too much....(hint-hint) unless you wanna sleep forever...