I've had 625 Carters, 600 vac. sec.s, 750 vac. sec.s, and now just put a set of worked 660's on mine. Haven't had a chance to try it out yet, but the 600's sucked big time, 750's didn't work well either. The 625's worked nice. Now like I said the 660's haven't been run much yet. As yoy can see in the picture, they are really worked over. Throttle response seems good, but like I said I really haven't driven it much yet. Let alone run it at the strip.