Can I remove, plug or make the EGR inoperable to gain mileage and/or HP.?

I've heard to plug the vac line going to it. Some people do it with a BB pellet, that way everything is still intact, and , to the naked eye, makes everything look like it is operational.

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1989 300E 144K

yes, but make sure it isn't already stuck partway open. Pulling and releasing a vacuum on it, you should be able to see the valve stem move, IIRC.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.