ECU ground - comments please

[thyrsted2@olsy.dk (Kenn Thyrsted)]

Scott Mockry's GREAT site shows this pic of ECU ground:

http://www.teleport.com/~scottmo/ecusys.html#ingnd

You can clearly see two wires.
On my IM there is only one !

Should there be two ?
Has anyone experimented with a seperate ground wire (from battery) here, and
will it cause ground-loops thus f*cking up the ECU ?

Engine starts OK, Cranks fine, but has performancevariations.....

TIA
    Kenn Thyrsted '87 200TQavant