Try and do this with friends. The only possible way to get this is to strip all your armour off until you have 100% mobility. Easiest level i found was the casino, rappel down the elevator shafts turn left and down the escalator and make a b line straight for the intel. grab it and GO BACK THE WAY YOU CAME, there is not enough time to go through the offices and you will probably get shot anyway. Run past the lift shafts you came down and head straight for the ropes on the windows in the slot room, shoot the window on the way to savetime. When at the top of the rope run like crazy and GET TO THA CHOPPA.