That gas smell... any suggestions?

i have cheap long tube hooker headers, which, from the collectors extends 24" to 28" cherry bombs, and then into a 12" pipes, which exits out under the rear seat.i have a 40 year old trunk seal and i have never smelled fumes inside the car. there are even holes in the floor from my old bench seat mounts.im guessing you have a slight fuel leak or an exhaust leak up front.