Hi guys, I own a w116 450 SEL non 6.9 and I have this problem: whenever I press the accelerator, around 2000-3000rpm the car doesn't go anywhere and stutters miserably and after it zooms ahead, making it a very unstable ride. This occurs at all the gearshifts. I've taken it to my local dealer and they haven't been able to pinpoint the problem. First, replacing the throttle switch and tuning it up. Nothing has worked. Does anyone know what could be the problem with the car?