I've got the same 95 E300D with 103K miles. These vehicles do have a kickdown lever to the transmission which drops the AT from 4th to 3rd when you floor the accelerator.

Even with the tranny dropped to 3rd, which I'll do manually via the gear shift sometimes when in mountains and hills to keep the tranny from "hunting" back and forth between 3rd and 4th, you're not going to see great acceleration. It's the nature of the beast with the non-turbo six cylinder that does not put out a lot of HP.

I do my best to "drive ahead" and anticipate needed changes in engine speed and bring the engine up to more RPM's before I'm bogged down. I've driven all over northern NM and CO and not had major problems.