Here the increase of speed might not be the problem at all. The ISPs have servers that don't allow you to exceed the speed once it's capped to a certain limit. It doesn't matter which applications you use or tweak, the computer will always download or browse to the maximum speed set up by the ISP. In some cases, turning off firewall, replacing old hardware with powerful parts, or opening ports increases the connection, decreases latency and makes the speed stable all times.