Either, or, or both depending on gearing. Adding a CVT is like adding gears. Gear low, you get more torque. Gear high, you get more speed. Find the right ratio, you gain a bit of both. Bear in mind that even a CVT only adds so much, it doesn't perform miracles. If you're looking for a tire-fryer, gear maybe 6:1 or lower and forget about that 50MPH. Still need more vehicle info to narrow it down.