Add the chicken breasts to the Instant Pot on the trivet. Pour in the chicken stock. Season the chicken with 2 tsp chili powder, 1 tsp cumin, and salt and pepper to taste. Add the pressed garlic. Pour on the juice of 2 limes. Secure the lid of the Instant Pot, making sure the valve is set to sealing. Pressure cook on high for 15 minutes and do a natural release for 10 minutes.  Quick release any of the remaining pressure. Drain half of the liquid from the Pot. Remove the chicken from the Pot and shred.

You can return the chicken to Pot and turn the Pot on Saute mode and add the remaining lime juice in and saute the chicken in the Pot.