Even untimed, 180 is pretty impressive. That means you're really developing the techniques necessary to solve the questions. Do a few more completely untimed, then gradually speed up. Your first timing can be an hour or more, no problem. Increase it gradually by 5 minute increments, and you'll eventually get it down to formal test time, while still retaining good accuracy.
The other thing is to focus on strategic test-taking. You know you can be accurate when unrushed, so focus on the 2 or 3 easiest games or passages, and do those well. Skip/guess on the last game(s) and passage(s). You only have to solve 1/2 the questions, and guess on the rest, to break 150, and you only have to solve 2/3, and guess on the rest, to approach 160. So if you stop trying to hit all the questions, and devote that time to the easier games, passages, etc., then your score will probably rise quickly.