If it is a raw gas smell, then check under the gas tank up front for any leaks. Remove the front passenger side wheel for easy access to check on things.
If it is an exhaust smell, then make sure that the engine heat shields are in place (if you open the engine hood and look down in there, you should not be able to see the ground). Re-check the exhaust fittings everywhere for leaks (you might see some carbon shadows on the tubes if they’re leaking....maybe).
What type of exhaust system do you have? Some exit right out the back and some exit off to the side. Straight out the back seems to minimize smells, but not always.
Give us a little more detail about the exhaust system and maybe we can help more. I have the rear seat covered by a tonneau cover and only get the exhaust smell when I stop for a light or stop sign and then almost always.
So you smell exhaust always while driving or just when you pull up to a light or stop sign?