front end vibration

[antmad]

My 1999 S80 shudders when accelerating quickly(just briefly), however under slower conditions the ride is smooth and normal. The entire front suspension has been replaced, and there are new brakes and rotors, too. I recently had the four of the engine mounts replaced and a part of the driveshaft as well. All to no avail. The sudden shudder is still there and I am at a loss. Please help.

Tony