Right, the cars did not stink when they were new. When the window is opened the inside of the car becomes negative pressure sucking air in anywhere it can. Check hatch seal, taillight gaskets, signal bulb sockets, rubber body hole plugs in rear hatch floor area, rust holes in spare tire well, gromets around emission hoses behind the rear interior panel, leakage thru rear hatch latch into rear hatch (pressboard cover panel is probably warped and leaky by now), quarter panel or inner fender well rust holes, exhaust system leaks near the shifter boot, etc. There are a lot of possible air entries on a 30 yr old car.