Exhaust leak on my 93 4x4

I think I have an exhaust leak? It must be coming into the cabin cause every time I drive the truck I have a bad headache. Sometimes I roll the window down a little and I get less headache. I think the exhaust fumes make me dizzy. But no headache when I am off roading with the window all the way down
Any way to check?

 

Found the leak. Hopefully this new gasket will seal the leak

 

Good job troubleshooting.

 

Change it but still have a 20% leak compare to the old
Will get a permetax copper exhaust to seal it