I notice the same thing, it comes from the plastic piece that joins the 2 panels.

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2004 BMW X5 3.0i
BMW 4.6is Wheels | BMW 4.8is Bumper/Flares/Valence & Graphite Interior Trim | ECS Cross Drilled & Slotted Rotors | Hawk HPS Pads | Toyo Tires
Pioneer Rear View Camera | Blackberry BT Music Gateway | Gauge Trim Rings | OSRAM Nightbreaker Xenon Bulbs | Smoke Side Markers
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2001 BMW 330Ci
2001 BMW 325Ci
1997 Acura NSX-T
1993 Mazda RX-7 R1