In addition, if you have not replaced the front and rear sway bar bushings, you should.
In handling terms, the opposite end often feels to influence the other- if the front sway bar bushings are shot, it will allow wallow influencing the rear.
Wagons are taller than sedans and have more mass resulting in a higher CG (center of gravity). This is why the wagons have beefier sway bars.
Replacing the front and rear bushings are inexpensive and definitely a DIYer project. Additionally, check the rear sway bar links. They are verticle plastic pieces that also wear. Just a small amount of wear translates into weird handling.
Keep us posted,
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
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'65 911 Coupe (#302580)