Yeah I don't have a track but I've certainly found this FPS drop (I'm running a pretty high spec PC, at 60-90 frames on Syria with high gfx settings) when using TEL mode in multiplayer: 1) With myself and a friend on a server he was hosting on his midrange PC, running Caucasus 2) Enigmas Cold War server with a decent number of players on, on the Syria map.
When switching into TEL mode, especially if there are maybe 2 contacts within range, though I've seen it with one only, it can cause some harsh FPS drops to under 25 for <1 second and then it goes away (Though for my friends lower spec PC it can be multiple seconds of huge FPS drop to <10 fps). Manual Lock-On seems to be fine. I'm not sure if aspect has anything to do with it, but found locking HOT bandits quicker and without FPS drops, whilst possibly cold/beam bandits cause some more fps drop? Although this could be a red herring and perhaps aspect has no impact.