The new edition Whizzers use 3 different pipes. The WC-1 and early NE motors. A slightly larger version used on the NE motors, and shorter version on the later NE and SE motors Ambassador, NE-r].
The best for street use is the slightly larger pipes used on the NE motors. The short pipes don't have enough back pressure and must have the insert to run smoothly.
My highest tuned motor has the NE pipe with the echo chamber cut off [about 1/2" ahead of the chamber and cut at a 45 degree angle].
Have fun,