vibration after frame replacement

Some time after the frame was replaced under recall I would intermittently get a rumbling noise and wheel shimmy as I approached highway speeds. Most of the time it goes away if I slow down, apply the brakes, and resume driving. Under the worst instances like accelerating up a long incline it also feels like there's a drag that feels like loss of power. Other times it drives like new instead of having 200K on it. Happens with summer or winter tires. Balance and alignment have been checked more than once along w front and rear brakes. Toyota even replace the U joints even tho the propeller shaft was replaced with the frame. The entire front end has passed muster at two garages. The shaking does not stop w the clutch pedal down or change of gears. Wondering if an ABS unit could be deploying when it shouldn't, since tapping the brakes often makes it clear up. Baffling!