Pat dry pork with paper towels.
Combine in a small bowl the RUB ingredients, whisk to combine.
Sprinkle the rub all over the pork. Using your hands rub in into the pork well.
Turn on IP on SAUTE, once hot add 2 tablespoons olive oil, and when the oil is shimmering add pork (in batches) and sear for a couple of minutes on each side, or until golden brown. Set aside and sear the next piece. Set aside the pork on a plate.
Combine the sauce ingredients in a bowl and add to the IP, use a wooden spoon scrape the bottom of any bits that stuck to it.
Place pork pieces in the IP in the sauce mixture.
Add some fresh rosemary if using.
Put the lid on in the locked position with the steam valve closed.
Set to PRESSURE COOK for 15 minutes.
When cook time is up, allow the pressure to naturally release for 10 minutes, then turn the steam valve to the venting position and release any remaining pressure.
Remove the lid and using tongs, transfer the pork tenderloins to a cutting board, cover with foil, and set aside to rest.
Switch pressure cooker to SAUTE setting and discard the rosemary.
Once the mixture is boiling, stir cornstarch into the 4 tablespoons cold water until dissolved, then pour into the instant pot and stir until thickened into a glaze.
Turn off IP.
Slice tenderloins, then serve with balsamic glaze on top.
Garnish with chopped parsley and some rosemary.