Your 2-stroke motor is an air pump. It moves the air in pulses or charges. The spark plug fires and ½ of the stroke generates power. The exhaust port opens and combustion gas starts down the pipe at supersonic speeds. The cylinder pressure drops, and the fresh charge transfers thru the transfer ports, over the top of the piston, and out the pipe a little. Now, when the pipe is working, the wave hits the end of the pipe and reflects back with enough force to push the unburned charge back into the cylinder before the piston closes the exhaust port. This is the supercharge effect generated by a good pipe. Compression occurs and the sparkplug fires before TDC to create maximum pressure after TDC. At 8000 rpm your engine fires 133 times per second!    Not much time to move the air required for top performance.
The basics are: More Air = More Torque. More air at a lower rpm = more torque available.

Casting marks, machined edges, and Nicasil protrusions in the port chamfer area, all slow or disrupt the airflow. Cylinders need to match the crankcase, and the airflow from the reeds must reach the base of the transfer ports without restriction. Careful work to smooth and match the surfaces will improve the airflow. Crankcase porting work improves performance from idle up to full throttle. Most noticeable is the bottom end torque, and faster acceleration.

Great improvement with Crankcase Porting: Ski-Doo (Rotax) 670 & 583
Arctic Cat 700 & 1000 T-Cat     Yamaha 700 SX-R Mtn. Max