Inspired by Adam's results, we picked up a 2.5 lb USDA Prime tri-tip from Costco. I marinaded the tri-tip for two hours before cooking and included the marinade in the vacuum bag.
The marinade is pureed onion, garlic, extra light EVOO, red pepper flakes, salt, and pepper.
I cooked it for 8 hours @ 130* and then seared it for 60 seconds on each side in Duck fat.
I think this is the best tri-tip I have ever made (I usually grill them). The meat was tender, had a great texture and mouth-feel and was very juicy.
