Before you mess with the ALDA, it would be much easier to first check the crossover valve. It is mounted on the cowl. There is a line coming from the rear of the intake manifold, around the back of the engine and into the crossover. Another line goes out from the crossover and leads into the ALDA.
This line and the crossover itself are susceptable to getting plugged up. Once plugged the ALDA will no longer increase fuel flow into the fuel injectors when the turbo winds up. Therefore no power at acceleration.
To clean I just removed the crossover and turned it upside down and sprayed carb cleaner into it until I could blow through the opening. You will have to get a 12 volt line to the crossover to get the thing to open up the waste gate. The purpose of the crossover to to limit the pressure coming through that line to something like 1.1 bars, or close. Anyway I had the same problem with my 81 SD and read the threads about the ALDA and found that to be the problem.
Just my .03 cents worth.