Check the obvious...manifold gaskets and flanges after that.
Unless you have a stout tailwind do I agree with backwash or turbulence...unless the entire exhaust system is degraded or the pipes dump out under the body somewhere.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
