Combine flour and sour cream. Dissolve bouillon granules in water. Add beef bouillon to flour/sour cream mixture, mix together and set aside. Slice sirloin across the grain into bite-size strips. Heat oil in a large skillet over medium heat. Stir in half the meat and cook till done. Remove from skillet and set aside. Add remaining meat, mushrooms, onions, and seasoning. Cook till meat is done and vegetables tender. Drain excess grease. Return all meat to skillet. Add sour cream mixture. Cook over medium heat till bubbly, about one minute. Remove from heat and let stand 2 to 3 minutes before serving. Cook egg noodles according to package directions. Serve stroganoff over warm noodles.