Sounds like background noise to me... My exhaust does the Shrinking ticks after turn off, but not when running and never with as regular rhythm as that.
Could be loose / dry solder joints in the AFM? could explain intermittent randomness.
There is a DIY fixup thread around here somewhere...
ahh, there it is. --->> Click this!
Should be along the same lines for RB25.
Looks awesome. What's the deal with street use? as in, can you use the Harness or does it have to be normal seatbelt?
For comfort, is the harness easily tucked aside? etc...