If I remember correctly, the 2.6 does not have flex disks as the 2.3, so I would look at the tranny and differential mounts.
The symptom of my bad subframe mounts was a "wandering" feel while stopping/turning/wind. Also, look at the gear stick when coming to a hard stop -- mine was moving around. Cheers, Andrew Seidel.
85 500SEC Lorinser
83 300D Turbo