I just got this servo for my vta touring car what is the capacitor they included for?

Savöx servos are notorious for their high power consumption. Depending on your ESC's BEC and your radio that can lead to brown-outs. The capacitor is probably supposed to help with that.

They used to be notorious. But pretty much every performance servo I have actually draws more than my Savox ones.

So what's your theory on the capacitor then?

Their servo is a 1251MG. None of mine came with the capacitor. Might be a special bundle as a result of the historical reputation.

Should I plug it into something? If so....what?

You plug it in your receiver. It will help in case of sharp drop in voltage supplied by the ESC's BEC. Under some circumstances, the current draw from the servo may get higher than what your ESC can provide. That will cause the voltage to drop and may cause your receiver loose signal. The capacitor acts like a buffer and helps to keep the voltage high enough so you don't loose connection. It won't help if your servo constantly draws too much current, but it will take care of short drops.

Martin Paradis

What ESC are you running? If you do end up using the capacitor, then plug it into the receiver, but you might not need it depending on the ESC BEC capabilities.

This capacitor will help to protect your receiver not shot down during the High Amper consumption. but if your BEC good enough, then you dont need this capacitor