Hey there. Would you mind downloading HWMonitor from www.cpuid.com, and checking the temperatures right after severe drop in FPS happens? It's most likely overheating.
I looked at the temps and it is only getting around 40-45 degrees celsius while playing battlefield 3 on ultra. So I don't think it is overheating. Could it be a bad update or something, because this all started to happen after I downloaded an update for origin. Could the origin update effect games like gta iv, because gta iv is also having low fps.