Jeff, I've noticed significantly more of this sort of noise in the TEs, actually. While road noise is probably less than what you'd find in your minivan, or in my dad's Previa for example, this resonating boom is quite bit more noticeable in the MB. I've recently driven a slew of Volvo wagons, a couple of TEs, in addition to ours, and a Camry wagon for good measure. Road noise is up over the sedan counterpart - but not the boom. It's not even as noticeable in the 123 wagons. I'll chalk it up to poor design given its consistency of occurrence, but I wonder if there's a way to reduce it a little? The TEs are some of my favorite MBs.