oldsouth,

Here's what I would do. Find a replacement ALDA, new or used. Find a g-tech or similar make friends with a shop with a chassis dyno. Mess with the replacement ALDA to your heart's content and do the forum the favor of posting your g-tech or dyno results.

I'm not sure about the 603.97x but on the 603.96s the intake manifold has to come off to access the adjuster on the ALDA. Much quicker to pull the ALDA and add shims or adjust it on the bench.

Come to think of it, if all you're going to do is add shims, then that shouldn't alter the factory setting in a way that can't be easily restored. But make sure you have an objective way of measuring the results. I wouldn't call checking absolute top speed objective.

In a nutshell, do what you must but don't break the seal on your known good ALDA.

Sixto
91 300SE
87 300SDL
83 300SD