To test leakage you need a MityVac to pump it up to 15psi. It should hold 15psi and not leak down. A bad (leaky) ALDA will either leak very fast or won't let you build pressure at all. If yours really is OK, the next stop is probably an ALDA adjustment, but I doubt that will cure your problem. Next item is to adjust the internal full-load fuel stop but that is HARD to do, may require removal of the injection pump. And at that point you might as well just take it to a Bosch shop for a full calibration. or your problem could be something totally different like a clogged air filter, low boot pressure, clogged exhaust catalyst, etc... you really need to do more dianosis first.
For ALDA adjustment, doing it with the ALDA in place and the manifold installed is a nightmare. On the 86/87 turbo diesels, it is MUCH easier to simply remove the ALDA from the IP, adjust it in hand, then re-install. I think that applies to the 1990-up turbos as well. It just unscrews from the IP (the nut underneath turns), but you may need to disconnect a couple metal injection lines for clearance (my one car doesn't require that, my sister's car does).