It’s impossible to legally modify a motor to “speed it up”. What you may be referring to is the fact that the motors FIRST gave us in 2005 weren’t designed to run at 12v (Were they 9V or 6V?). Some teams decided to run them at the full 12V and run the risk of frying them, while some teams just operated them at the reccomended voltage.
That’s not an issue this year, as the FP motors are designed for 12V.