Volkswagen Repair: timing light attachment for Digifant system, battery power supply, spark plug wire

Question
Hi Paul,
I have the Bentley and use if with out '91 Jetta with the RV engine (8Valve) and Digifant I control unit. In the Bentley there is a rather incomplete description about attaching the a timing light to check and reset the timing. It says to attach the timing light to the + post of the battery and to the - post of the ignition coil. I have assumed that refers to the battery power supply clips, and that the magnetic pickup for the #1 plug wire is used as is routine. Does that sound correct to you?
The reason I wonder is that when I do it that way and then time it to 6 BTDC at 2000 rpm the resulting timing is way off, so far as to be almost undriveable. So instead I time it to 6 BTDC at idle speed. What has been your experience with timing the Digifant? I understand that it may not be too important where you have it set becasue the Digifant self-adjusts the timing. But why not just hook the light up to the battery, rather than have the - clip on the coil -?
Is there some reason for involving the coil in powering the light?

Answer
Roland,

I think they've made a mistake in your manual, the connectors must be connected to the battery pos and neg. I've never connected any timing light to the coil, your signal comes from the magnetic pickup,from the #1 spark plug wire.

Secondly, set your timing at idle, not at 2000 rpm, you're right on both counts.

Keep up the good work,

Paul