Wood chunks maybe too large...try a cook without extra wood and see what happens...it will burn clean...then try adding smaller chunks or chips and go from there...
I don't own a WSM...but you need to establish a base line...My .02
"Before the end of this thread, someone will tell you to build a UDS"...Nostradamus
Lang 36 Patio - Kamado BigJoe
30" Gasser(Dock Box)