Hey,
I've been struggling with an issue lately where i hear this repetitive ticking noise when decelerating or under light load (cruising at around 1-2.5k revs).
It kind of sounded like a light piece of metal tapping something, so i have gone through and checked and tightened the heatshield.
The car does have a 3" downpipe on it, but it isn't that knocking the chassis, that is a different noise
Hopefully someone has had this before, otherwise it might drive me insane!