I've been playing Mario Kart 64 with my brother recently, actually, and it's amazing how vastly the placements vary when playing with 2 players. Like you said, it does come out pretty preset if you're in the lead and no one else is playing, though. Then again, there's always the odd flukes where some character in the back of the pack suddenly accelerates to 20% higher than the max speed and finishes a lap ahead for no apparent reason.
On that note, it's funny how the end-of-race placement varies by installment; in MKDD, the computers will adjust their speed however necessary to keep the racers in the order they finished in, but in MK64, if the top few CPU's were gaining on you at the end, they'll pass you up by half a lap in no time flat.
