Lectron first introduced the High Velocity carburetors in the 1970s for road racing when bore size restrictions were imposed to slow the bikes down on long straight aways. Ironically, they maintained nearly the same MPH while turning faster lap times! This is due to our more aggressive High Velocity bore taper which creates faster air speed for quicker fuel pickup, more bottom end and mid-range, while still revving out like a larger carburetor.
The High Velocity carburetors have been used in motorcycle drag racing for many years, and applications like karts, sprint cars, ATV drag, etc. where heavier fuels (like alcohol) need more lift to achieve the required response and make the most power off the line. In 2016, this technology was made popular for the 2017 model year KTM and Husqvarna dirt bikes with the balanced engines.
Notice how the 38HV has the same inside diameter at the center of the bore as the 36, but the same inside diameter on the intake side as the Standard 38. This allows it to make low end power and respond quickly like the 36, but rev out well like a standard 38.
If you are looking for that peak HP, need max overrev, and are more focused on wide open performance, you might consider the Standard bore Lectrons over the High Velocity.
If you are running a dirt bike with a balanced engine, a big bore kit (like a 144), a flywheel weight, or need more grunt and mid-range to get out of corners faster, the 38 High Velocity could be the right carburetor for you. Consider the 38HV as an intermediate between a Standard 38 and Standard 36. Ridden back to back, the 36 and 38HV will feel almost identical until you reach the mid-range which is where the HV will feel like a standard 38.