Pipes are made to run at given temp, about 625 deg in the mid up to 1450 or so on the top. That is what controls the speed of the ultra sonic wave that regulates the pulse to the carburetor through the cylinder. Hotter gases are faster to travel through, so the wave speeds up. Ceramic or Nickle coating is an insulation. So longer to heat, slower to cool, and higher overall temps. That makes the sonic wave travel at a higher speed, and carries more heat back to the piston, the hot metal then repels the new charge coming into the engine. The sonic wave returns too soon to charge the cylinder when the gases are super heated in an engine is tuned to make maximum horsepower at high RPM. Every one who has a dyno will be able to verify this. Raw Steel pipes at cooler temperatures will yield better and more consistent power over coated pipes at higher RPMs.
Ever see a professional motocross racer running a platinum pipe? Nope. Woods/enduro that tune the engine for torque (gnarley pipe as well) they get a hotter pipe at lower RPM and that favors the motor build they have for that kind of racing with plating.
Ceramic on snowmobiles loses HP also, but super consistent pipe temperatures are critical for clutch tuning to hold the engine at maximum HP at a specific RPM. If the pipe temp changes that target could vary a few hundred RPM and the clutching is no longer inline with the engine's peak output. So sacrificing some HP to have stable RPM/peak HP maintained is a reasonable middle ground.
Snowbikes, specifically I've learn in the past few seasons don't need grunt. They are geared so low that any hard pack is a walk in the park for any size engine. But deep powder and long high altitude runs at speed require high RPM HP. Hence why 4 strokes that rev to 12k are winning popularity over the two strokes out there that rev to 8-9k... yet I dropped my 17 450 KTM for a CR500 this year - cause I'm a 2 smoke lovin A-hole.
I hope that helps break it down.
