Be sure to periodically clear the sunroof drains in the four corners of the tray. Start off by vacuuming out whatever debris you can then use compressed air to blow the drain tubes clear. You can try using a short length of vinyl tubing to reach the back corner ones. If needed you can try reverse flushing, finding the ends of the drain tubes up inside the drain slits in the front fenders or where they join the rear cavity drain hoses up in the corners of the trunk or up inside the drain slits at the base of the C pillars in wagons. If needed you can flush with water.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now