Hello everyone,
i read that some people happen to have unexplainable and sudden FPS drops in 40-20 zone + additonal audio stutter. I had this too until i found the cause of it. Now before that i reinstalled apb 2 times, defragmented HDD, downloaded new nvidia driver and nothing helped. What did help was unplugging my USB game controller. So if you happen to have any additional USB devices connected - remove them and see if it helps.
Also this problem was only noticeable in APB. In other games I didn't notice anything weird going on.
cheers