The P0400 EGR malfunction code came back, so I replaced the valve and the tube. Problem solved.

The only advice I can offer is that the tube is fairly easy to remove and clean out, so I wouldn't replace it as a matter of course. If you do replace it, be sure to get the little compression fitting that goes on the valve end of the tube. There are also two gaskets that should be replaced. If you remove the connector on #3 fuel injector, it makes it easier to get a socket on the front screw that holds the valve to the head.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe