That "thing" is the overboost sensor that shuts off the Alda if the turbo is crankin' out too much pressure. You may just need to supply switched power to it (i.e. supply juice to it when the ignition is "on", but I'm not completely sure on that front).

There was a huge post on here not too long ago - about six pages - about someone doing a turbo conversion, s/he'd be the one to ask. Or DieselGiant....

Jay.

P.S. (Being lazy) how'd you do the throttle linkage? Got any pix?

__________________
On the road, currently:
'83 300D (German spec.) 168k mi. - - Wolfgang (tucked snugly away for the winter!)
'87 300D 375k mi. - finally went over to "The Dark Side"
'87 300TD 225k mi.
Cannondale 66cm CAAD5 w/Campy/Jamis Aurora
Hujsak Custom Fixie/Landshark Track Shark Custom/Ahearne Custom 29'er