My comment is eight months late, but I have some experience to share on the top of E430 air passages getting clogged. I changed my valve cover gaskets and discovered air passages in the valve covers were completely blocked. I had already changed my EGR valve in response to Check Engine Light. No problems with E430 vacuum or exhaust gas issues since.

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1962 220Sb ~ The Emerald Bullet http://www.youtube.com/watch?v=hx6tN1W48_o
1957 Ponton 220S
2001 S600 Daily Driver
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