I have avoided Sydney the most as I could, for the last week, and I haven't had a single memory leak. When I go in and out of big cities, my FPS lowers every time I go in until I restart the game. As a cop I had to go in Sydney a couple of times, in the beginning it seems very bad but once the city renders more the FPS goes a little up again, but it's definitely lower than before you came in, and that also sticks to the game even after you have left a city.