does anybody know why the glow plug light would flash after engin start is it a sensor or engin management any info greatly received many thanks

On some of the older models, the glow plug light doubled as a bulb out warning?

Chipping or tuning boxes can also cause engine management prob's.

on the A4 chassis (not Audi A4, but MKI A3), it is usually a sign that the brake light switch is faulty.