95 e320 Wagon Steering / tracking.

This past winter I thought the MB dealer cured the alignment problem because it didn't pull to one side, it ran straight [kindof]. I attributed the sllght wiggle to the new snow tires. You don't notice it cruizin city streets. But on the interstate when going straight, you feel a slight self-correcting wiggle that is about 1/4" steering wheel movement.

Winter's come and gone, the car was rarely used since the alignment, but now my job requires it to be interstate capable.

All the bushings appear to be ok, nothing's bent, good tires and wheels.

2 years ago when the original steering box began leaking, a new steering shock and reman gearbox were installed by an inde shop. Today I crawled under it and really looked at it. The gearbox has 4 mounting points, but only 3 are used.
There is about a 2mm distance between the car body and the unused [no bolt] mounting point [top front]. The 2mm distance is about the same thickness as the washer used on the other 3 mounting points. Is this correct? I would think all 4 points should be pressurized to absorb the amount of torque the system handles.

Your thoughts are appreciated.

Bob