Find the Throttle under Config -> MIDI.

What Does Throttle Do?
The throttle adds a delay in between sends if more than a certain number of MIDI messages is sent. In version 1.6.5 the delay looks like this:
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Max messages before delay: 5
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Sleep between batches: throttle (1-15) times 10 milliseconds.
So, a throttle of level 2 will delay 20ms between every 5 messages.
Note: Throttle only works for Batch sends, which include send-all and preset-sends. Presets for groups are not included.