[yorkie_chris]

Race exhausts are ones with perforated tubes down middle. Idea is the sound waves can be damped out by the packing around the outside, but the straight-through design does not present an obstacle to flow.

Standard ones tend to have solid baffles and convoluted paths for the gas to slow and expand the gasses without robbing too much power. The standard systems are actually pretty cool on modern stuff how they manage to get so much power and still make them quiet. On old bikes standard pipes were like a cork up the back of it!