ORIGINAL: revelation
What you said before about the foil is a great idea but maybe think about screening the actual glow plug lead with it??? I have some EMF screened cable here from work which is just that. Some cable with a foil or braided wire screen around it.
rev.
I'm sure I can find that here somewhere. I will try it to see if it cuts down the 'slight' and infrequent jitters I still get.