It sounds like something is binding. If you disconnect accelerator linkage ends under the hood one at a time, you'll be able to figure out what's giving you trouble. This would also be a good time to lubricate the linkage, if you haven't done so already.

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1982 300D, black w/ palomino leather, 203K
2001 E320, champagne, 105K (Mom's)
1999 Dodge Dakota, squeaky & battered, 142K