[dave5358]

Looking for thoughts on what might be causing this, or what it sounds like to some of the more knowledgeable folks on here.

Ticking sound coming from driver side of the engine.
I can't hear it right off after a cold start-up, it seems to kick in after the engine goes to low idle <snip>

It could be a variety of things - some very serious. But you might start by checking your Fuel Line dampers. You should have two of them - small 2" round gizmos located by the driver's side wheelwell:

When they start making noise, you can hear it inside the vehicle much better than when you're poking around under the hood with the engine running. The way to test them is to get a long metal rod or a long socket set extension or even a long screwdriver. Place one end against your lips and touch the other end to the damper. If the damper is "clicking" you will know it!

These devices are deathly expensive from the dealer. If you search the net, you can find them much more reasonably priced (but still expensive). Regardless of how the new damper(s) come, replace them by removing the clamps - visible in the picture (looks like they have some blue Loc-tite on the clamps). The small hoses are very tight, so work slowly and carefully.

BTW, even if it's not the fuel line damper, you can still use the rod-to-lips technique to more carefully locate the source of the ticking.