C-One only sells gears, and they're about as expensive as the C2 tranny (especially because of the complicated install), which is way stronger. The gears would be bad for a turbo, anyway, because they make the gears even shorter. You'd waste time from continually shifting. Gear ratios that close are unnecessary for a turbo car because a turbo gives you a much wider powerband. The only thing the C-One gears are good for are NA GTS', since they'll allow you to land in lift all the time.