Place your immersion circulator in your preferred container and fill with enough water to submerse bagged tenderloins. Heat water to 145°F.
Trim any excess fat and silverskin from tenderloins and rub with half the pepper and a pinch of salt.
Place pork tenderloins, garlic, rosemary, and red pepper into a heat safe plastic bag. I usually put put in one tenderloin then add the rosemary and garlic then add the other tenderloin.
Squeeze out the excess air or vacum seal your bag and place into the heated water.
Cook for 90 mintues to 2 hours making sure the bag stays submerged the entire time.
Remove tenderloins from bag and discard rosemary and the remainder of the bag. Pat tenderloins dry and allow to sit uncovered for a few minutes.
Rub lightly with oil and sprinkle with remaining salt and pepper.
Over a very hot grill or in a very hot heavy skillet sear each side of the tenderloins, rolling and moving frequently, until browned. This should be done over high heat and be done quickly enough not to overcook the tenderloin.
When it comes to adding flavors a little goes a long way when cooking meat sous vide, both garlic and rosemary can overtake the pork so don't over do it.