Derrick,
Next time go with fewer chimney coals 8-12 at the beginning. With external temps what they are around here, I'd close my bottom vents to about 50 percent when about 50-75 degrees from target pit temp. Then to 25 percent or less when within 25 degrees or so.
As mentioned above, the WSM tends to cook hot until it's seasoned a bit. Also, I've noticed that external temps are important, especially in open sun. I had to cut a shade tree in my backyard and now my WSM is in direct light. I think (know) it's cooking quite a bit hotter.