Hi,
Did you have this problem of different motor speed as you developed your sketch.
Did you write a sketch just to run the motors forward, then develop it to turns.
That is did you program your sketch in stages, get each stage working correctly then program the next stage, and eventually join them?
OR did you try and write it ALL at once.
If you used the first method then you must have code that PURELY runs the motors.
Go back to that and see if your motor speed diff problem exists.
You need to program a basic sketch to check this problem, only controlling the motors.
Tom.... 