Are you highlighting the cabin vents?
If so then you are moving enough air with the subwoofers to cause the vents to try to expel it assuming it only happens with the truck closed.
08' IS-F M.M., SARD CUVU Evolution, FIGS Mega Arms/Toe Links, BC Wheels w/305s, FIGS 2 piece F&R rotors, BC/Swift Coils, FIGS Bushings, Cusco Bar, iCode/aFe , PPE/Borla, ARKYM diffuser, Vaistech, JL sub/amp, LED, Ultinon, Morimoto, JDM visors...
93.5 Supra Anthracite GT42R 857 WHP
08' E61 535Xi N54 Wagon M sport, M5 seats, KWv3, JB4......