Rigman,
The responses up thread have you well covered.
As dirtsailor mentioned, my "Go To' method for cooking roasts of any kind for many years is to do it in a cooker at the lowest possible temperature it can go to. For me, that's 150F in the smoker, and 180F in the oven. When the IT hits around 120F I pull the roast, double wrap it in HD foil and a heavy beach towel, then put it in a warm cooler for 45-60 minutes. The carryover will increase the IT 5F-10F. When getting close to serving time, I preheat an oven or gas grill to 500F+. The roast goes into the preheated oven for 7-8 minutes, then removed, rested for 5 minutes, sliced and served.
When I do a lean prime tenderloin such as you are, I make small slits throughout the meat's surface and stuff each slit with a mix made up of back fat, garlic, and fresh parsley or rosemary, all minced then pulsed in a food processor.
As mentioned, jus is always a good accompaniment, but my personal favorite is roasted and softened veal (or beef) bone marrow mixed with it's juices, and a little finely minced shallots, parsley, and capers. It's a bit decadent, but then, so is a prime tenderloin.
Enjoy!