Before you go too deep into the injection pump be sure it isn't something else with the ALDA. Do a search on ALDA. Try some of the (sometimes controversial) adjustments. I found that a half turn adjustment made a lot of improvment on my 225+K 2.5. Since you appear to have no fuel increase at all, you might try something more extreme. In any event, the vacuum may be fine but the mechanicals of the ALDA the culprit (collapsed spring). I'd want to be very sure the ALDA was truly functioning as it should before going deeper into the pump.

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Bart

2002 ML500, 2009 CLK350 Cabriolet
93 300D 2.5 Turbo 265,000 Miles (Sold - bad idea)