My Wagon has been idling poorly, but there are times when it idles so rough it shakes the car a bit. The other day I took a trip 350 miles each way. It ran fine on level ground, but when going up hill, it acted like it wasn't getting enough fuel. I took it to the dealer yesterday. They said that they couldn't find any problems, but that "maybe" if they changed the spark plugs and the $800 EGR that "might" fix it. I had them change the spark plugs, but wasn't ready to pay $800 on a "maybe." Today while driving it seemed to idle better overall, but at times the poor idle would return, and very poor acceleration, especially from a stop. For the first time, while taking off from a stop it felt like it was going to die, then it bucked and backfired twice before getting on its way. Does this seem like an EGR issue or something else I should look into? Thanks for any help!

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Mercedes Fleet:
2004 CL600 Designo Espresso SPORT
2004 S600 Designo Espresso SPORT/Lorinser Pkg.
1999 S320
1988 300TE
1972 280SEL 4.5
Diesel Fleet:
2014 GL350 Blutec
1987 300SDL Blk/Blk 4 place seating #18 head
1987 300SDL Smk Slv/Burgangy #17 head
1986 300SDL Blk Pearl/Palomino #14 head w/ 280K
1984 Lincoln Mark VII Fact BMW Turbo Diesel