Optional - marinade the tenderloin in the Italian salad dressing for 2 hours or up to 24 in the refrigerator. After marinading rinse and pat dry.
In a small bowl, combine garlic, basil, oregano, thyme, parsley, and sage.
Remove pork from marinade, rinse and pat dry. Generously season tenderloin with salt and pepper, as well as herbs.
Heat instant pot to medium high.
Add oil to instant pot, heat oil until shimmery.
Add tenderloin to pan, and cook on all sides until dark golden brown.
When Tenderloin has browned, but not cooked, remove and set aside.
Scrape up any brown bits from bottom of Instant Pot.
Add stock to Instant pot.
Add trivet to Instant Pot.
Place pork tenderloin on top of trivet, top with pats of butter.
Place lid on Instant pot, set to seal.
Cook on the High setting for 2 minutes (yes this is right - we're simply using the time to come to pressure to cook your pork tenderloin plus an extra minute.)
Let pork tenderloin naturally release, about 7-10 minutes.
Let sit 10 minutes before slicing.
Serve immediately.