That's a good question about the exhaust.
I went with a Brock Alien Head 2 on my Nitrous bike because I could tuck it most of it in behind the body work. However, I'm building an all motor 1340 bike and I'm going with a Brock 4-2-1 sidewinder. Even though it sticks out in the wind, I believe the 4-2-1 makes the most power in the upper RPM range and since I know the all motor bike will be slower than my nitrous bike (less aero requirements), the power should be an advantage.