Re: Exhaust smell in cabin, '06 XLT V6
Generally speaking, when an exhaust manifold gasket leaks, or the manifold is loose from the head due to broken or loose bolts, you will get a noise when the engine is running. It can be a chirp, whistle, or other spiky sound, especially if the manifold has a crack. The leak or crack can close up and quiet down a lot when all the parts are heated up.
If you don't have a noise, you don't likely have manifold gasket problems. I would look further down in the exhaust system, near the final catalytic converter or the 'flex hose' area.