From reading your first few paragraphs, check your exhaust pipes for holes or corrosion. If you have holes in your pipes, it can cause a loud noise and could be the reason why you smell something (does it smell like exhaust/gas fumes?)
Check your muffler and cat as well, just to be sure. If that's ok, then I don't know what else it might be, there are tons of things that could be causing your car symptoms.
Check your muffler and cat as well, just to be sure. If that's ok, then I don't know what else it might be, there are tons of things that could be causing your car symptoms.