The studs are screwed into the spoiler. The spoiler is fiberglass so don't go crazy on the torque. There probably is junk under it. If you take it off you will likely find dirt under it and a rub mark in the paint on the trunk lid, possibly some rust.
If you do decide pull it completely off I'd put a thin spacer on the studs between the spoiler and the trunklid when you re-install. I used some thin nylon washers on mine to give it just enough space for water/debris to drain out from under it yet not look raised up. I used some clear silicone on all the stunds on reinstall just to make sure I didn't introduce any leaks. So far, so good.
