[semlar]

It could be a nameplate addon due to the high amount of processing required to detect and modify them.

I think there's an addon that can help you gauge the amount of resources that your other addons are using but I don't know off the top of my head what it's called.

Oh one more thing, if an addon is throwing errors and you have them set not to display under interface->help then that could definitely be causing huge amounts of lag without telling you that something is wrong.