I ran into this a short while ago on my K7. I went through two sets of after market cables (including Motion Pro) before I learned my lesson and got a set of OEM. I could have botched the order, but with one set the nut was the wrong size and wouldn't seat into the throttle housing. On the other one of the cables was too short.
After looking at the after market set and OEM set side by side, the quality difference was clear to me. I know there are some folks who've had good luck with Motion Pro, but I'm a fool-me-once kind of guy and I'm happy to pay a little extra if I think I'm getting better quality. Not to mention all my wasted effort and time.