The original version of this reverse gallop palm-mute guitar lesson, given to a guitar student, were bars 3 and 4 played twice.
To work on speed, it would be beneficial to work up the original, or even play through the last two bars once instead of twice. Adding the two new bars adds an element of endurance to this exercise/riff.
Here is the Guitar Pro 6 tab for this lesson:
HEY!!! Does Your Rhythm SUCK!?