Yeah clicking a pen is a good way to describe it, the faster you here that the worse the Det is, if you only here "click" and then a few seconds later another "click" your just starting to Det, if it's "click, click, click, click" then your in trouble and need to let off immediately!!

I have bolted them to the coil pack bracket (old Dizzy) 10mm bolt, or on the inlet manifold, both sound pretty clear.