Try injecting one ounce/# apple juice prior to smoking. I start @ 226 then wrap in foil & rotate after 12 hours (during stall) and increase to 276 until they hit 200. Always perfect.
I buy my pork at Sam's and get rave reviews.
IMHO 16 butts is too much for a FEC100. (The 100 signifies it will cook 100#s of pork.)