Chuck and Tom thanks for the prompt response. I completely removed the entire intake and cleaned the sensor plate mechanism, replaced rubber plumbing for idle intake. The sensor plate moves easily before priming the fuel and is somewhat harder to move when the engine is running. The sensor plate is opening with the throttle plate, but it only opens a little bit and then it won’t move anymore and the engine starts choking and the vacuum goes down. I definitely don't have a huge air leak because when I disconnect the idle by-pass air hose and plug it at the air guide housing. So when I plug the by-pass hose the engine dies. I have a feeling that problem is with the fuel distributor, since it is to hard for the vacuum to operate the sensor plate. I checked how the sensor plate on my 420SEL felt like when it runs and it is alot easier to move than in my 280SL. I wonder if there is some kind of adjustment on the fuel distributor to adjust the movement of the sensor plate.

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Roman
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87 300SDL 152K
86 420SEL 228K
83 280SL 145K (5 spd)
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