User blog comment:SonicFan/Your Least Favorite YJ Episodes/@comment-5638184-20121019120608/@comment-130.18.47.253-20121019165945

Impulse was brought in because it allowed Wally to move out and be the guy on the sidelines screaming at Nightwing "HAVE YOU LOST YOUR (censored) MIND?! THIS A COMPLETE FIASCO AND YOU DRAGGED MY GIRLFRIEND INTO IT?" and because it gave us a plausible character who knows of Blue Beetles importance in the Reach's plan, and will hopefully prevent BB from being turned to the darkside.

I think Impulse is faster than Wally because Impulse was probably under a lot more stress in the future, and he could possibly have been the subject of Reach experimentation at some point. It could also be that he inherited Barry Allen's metagene which was activated to a different level than Wally's.