A steal driveshaft has memory. All driveshafts twist. A very small amount of that twist stays in any metal driveshaft. Over time this accumulates and eventually you will start to feel a vibration because now your metal driveshaft has become imbalanced. A CF driveshaft has no memory and always comes back to it's original form
Fred 95 300TT SGP Stage..Who knows..lol Dynoed 539.4 RWHP, 481.2 Lbs. Torque Pump Gas @ 17 Lbs. of Boost NO NOS!!