2000 Buick LeSabre - Shudders

My 2000 Buick LeSabre shudders when accelerating during turns (just before straightening out the wheels after the turn). Sometimes it seems there is a slight shudder even during straight accelerations. All suspension parts have been replaced: CV axles, control arms, ball joints, struts, tires, steering rack. Two different garages tell me motor/transmission mounts are good. The only thing not replaced are the sub-frame bushings. Could this be the problem or could a bad harmonic balancer be the issue? The car runs great (269,000 miles) and my wife won’t let me replace it.

I doubt either the subframe bushings or the harmonic balance are at fault. The balancer is very easy to check soo, go ahead but I doubt that is the issue.