Cliff’s notes: How do I disable/bypass the ALDA?

Description: Please read on –

I have had a new symptom some up on my ’83 300SD. When cruising above about 2,000rpm, I notice that once I pass about 20% throttle position, I am not getting any more power out of the engine. To put it another way – it’s like once you push the pedal in about 20% of the way, it doesn’t matter if you push it any farther, you are still getting about 20% throttle.

This started just a few days ago, and I made no changes to the car at the time this issue came up. I am going down my to-do list in order of easiest to check to hardest. I have replaced both fuel filters, made sure I had a full tank of fuel, and looked at all the vacuum lines. I also triple checked the lines for any air.

At this point, I am pretty sure it has to do with fuel pressure/delivery. Before attaching pressure gauges to check fuel pressure/vacuum (before and after the Lift Pump, respectively), I would like to disable/bypass/shoot to hell the ALDA. As far as I understand, this unit reads the vacuum/boost signal, and “feathers” the fuel delivery, as not to deliver too much fuel when you floor it before the turbo spools up. I would think that a faulty ALDA that always thinks you are under vacuum (read: turbo is never spooling up) even when you are under boost – would present the exact same conditions that I am experiencing. And yes, I know that the turbo is building boost (as I can hear a huge “whoosh” when I let off the gas and the EGR valve opens).

So I ask, how do you disable/bypass the ALDA? I remember some people talking about it disabling it, and just having to make sure and not give it too much throttle before boost (or else you’ll just bellow out fuel smoke).

On a side note, does anyone know an acceptable vacuum for the input of the Lift Pump (how much “sucking” can the Lift Pump do?), and also – what is a “normal” pressure right after the Lift Pump. I’m hoping that I guessed right with the ALDA, and won’t have to get to checking fuel pressure/vacuum…though I might anyways out of curiousity.

Thanks in advance for the help!

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1983 300SD ~250k