I'm assuming we are here talking about speed transferring files... If so then yes a newer USB 3.0 compatible flash drive will boost the speed at which data can be written and read from a external source...
If we are talking about speed like boot speed, internet, games, etc.... Then this is by far the dumbest thing I've ever heard.... The ONLY way to EVER make a computer operate faster is to upgrade the internal components and by optimization of programs. In the real world, the more USB drives you have in your system, the SLOWER it goes... Reason is: the system keeps checking if said device is requesting information/processes...