Multiple areas:
1). 4 and 5 irons. I had a very open stance which was adjusted by my local pro, however I still have a slight fade at the end of the shot. Additionally, these clubs are prone to more 'chunking' for me - hitting the ground 2-3 inches before the ball resulting in a mis-hit.
2). Consistent stroke on chips. I haven't figured out my chipping yet. I try to stick with a sand wedge, however my swing is vastly different when in close compared to further out. This has recently led to me hitting most shots long (landing the ball at my target rather then letting it release to the hole). I also have very little spin on shorter chips - I can't stop anything.
3). Core strength. Stomach, shoulder and back exercises have really helped my game. Hitting through more shots, better divots, etc. I'd like to keep it up through the winter to see where I end up next spring.