Yes, stronger springs for the trunk. You are adding the weight of the spoiler and the original springs wont hold it up. If they put the stronger springs on without the spoiler you would release the trunk and get bonked on the chin.
I ended up using the original non-spoiler springs with my spoiler because I liked the fact that the trunk did not pop open all the way if I hit the trunk release button inadvertently, leaving my trunk open all day at work. With the original springs the trunk would be open but not visibly open.