The last pitbox is 3 seconds per stop faster than the first pitbox, regardless of traffic. If you're in the last pitbox your driver flies through the pits at full speed without slowing down, stops, and then flies straight out the gate. If you're in the first pitbox, your driver stops straight away, and drives through the pits incredibly slow (as they should)
15 seconds gained over a race if you do a 5 stop strategy. This needs to be fixed asap :(