I just replaced the O2 Sensors but that still didn't do anything. One thing I noticed is that when I start my car up the timing is set to 35 degrees BTDC (I verified this both with a timing gun and in ConZult). As the car warms up and the RPMs drop then the timing is reduced slowly down to 15 degrees BTDC (when fully warmed-up). Around the 28 degrees BTDC mark the misfiring starts to occur (it intensifies as it drops down to 15 degrees BTDC).