Loaded up Patch 4 and played for about an hour and a half last night. My frame rate was much lower than normal. Typically in light traffic it runs 60fps, last night light traffic was running low 30s. In heavy traffic I usually run low 30s, last night it was running under 20. I was on center island with lots of gound vehicles, and heavy enemy aircraft. But I've never seen it that low previously in similar situations.
I will check it again tonight and see if the issure remains.