Well, I ordered the "Stealmycar" unit from eBay for my '91 W126.
I'll report on my success.
Constanza; I assume you gave up on the Stealmycar unit due to the unclear wiring directions they sent? (I don't blame you!)
But, I found a 2006 post by PTM6295
W124 1991 300E Keyless Entry Question).
His post has a wiring diagram photo, which compared favorably with Constanza's wiring notes. So, it appears this unit has the DLS-V relay set built in, and should hook up in the same 4-wire configuration.
We'll see!
PTM6295 reported the alarm triggered, however, so I may have to address this after I get the unlock going.
I know Chris and others had no alarm issues with their similar installs, so I'm hoping for the best.
Funny, I have a hard copy of the '86 W126 factory manual, and there are wiring diagrams, vacuum diagrams for everything, EXCEPT THE ALARM SYSTEM! Maybe they omitted that to keep the theives confused?
DG