With all the work you've been through have you tried to disconnect the sway bar links and tie them out of the way then go for a drive. See if that eliminates the noise. The noise you describe sounds like a swaybar moving. And like I posted before, the Hyundai Kia vans of that era were very known for subframe bushing failures. They were pretty obvious with a visual inspection or letting someone power brake or shift it with a long pry bar.