Set pressure cooker to SAUTE. Rub tenderloins all over with oil. Season generously on all sides with salt and pepper to taste, then dried herbs and garlic powder.
Use tongs to place tenderloins in the pot, turning over every 1-2 minutes until browned on all sides.
Whisk together soy sauce, brown sugar, balsamic vinegar, and water and add to the pot. Put the lid on in the locked position with the steam valve closed. Set to PRESSURE COOK or MANUAL for 15 minutes.
When cook time is up, allow to natural release for five minutes, then turn the steam valve to the venting position and remove lid once float valve drops down. Use tongs to transfer pork loin to a cutting board and set aside.
Switch pressure cooker to SOUP setting. Once boiling, stir corn starch into the 4 tablespoons cold water until dissolved, then pour into instant pot and stir until thickened to a glaze.
Slice tenderloins, then serve with balsamic glaze on top. Extra glaze can be stored in a jar in the fridge up to 2 weeks.