It could be the front lower control arms. There are rubber bushings in them that get worn out over time. I have the same symptoms and the control arms are a known problem on my car. It's the entire subframe moving around. I already checked my engine mounts/roll restrictors and they are fine.
Only problem, there is no way to upgrade them if you have the horizontal style like me. You can buy OEM, get a set from BAT, or wait for Haines Motorsports to come out with upgraded arms. If you have the vertical style, then HMS already can sell you a set with upgraded poly bushings.
