1991 300d 200700 on the clock I have no codes cleaned fuel system with bio and diesel purge made a great improvement, with direct vacuum to waste gate I can boost over 15 20 psi no problem installed new vacuum switch for waste gate and will not boost over 7 psi or so with old switch installed would not boost 4 psi. It does boost up faster now but it seems that the computer is requesting the waste gate to be opened. Boy I wish my 3000 OTC scan tool could watch data stream on this so I could see what the computer was thinking. Either way It don’t and I can’t. I have not codes and good vacuum everywhere. Any ideas thanks for your help.

You could replace the vacuum actuator with a traditional pressure actuator. Just look on eBay for something in the 13psi range.

The computer is much simpler than that. All you need is $20 in parts from radio shack to figure out what it's thinking. Go here and scroll to the bottom for the schematic and parts list. You're going to need to find the list of what the codes mean...I'll be able to get you a copy when I get home tomorrow if you'd like. Check and clear your codes, drive the car for a while, and check them again. See if any of them come back, and report back here. I did tons of diagnostics on my car's EDS when it had no boost. I finally narrowed it down to a bad wastegate vacuum transducer. The computer was throwing codes for a bunch of other stuff, but like I said earlier, it's really simple for a car computer compared to the standards for the last ten years.

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Dale

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1990 300D 2.5 Turbo -155k
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We have built the code reader and it has no new codes. He did adjust the throttle cable and it runs better but still not as good as it should or mine. It seems to keep bleeding off boost.