Need your guys help diagnosing a misfire.

We have an 05 Chrysler town and country with the 3.8, for the last 5,000 ish miles we've had a cylinder 1 misfire at idle. Only at idle, it will go away as soon as you speed up. It's never really been an issue but we decided to finally try and fix it.

We started out doing plugs and wires, swapping coils and fuel injectors, checked compression. None of those things fixed it, and compression was still good. I'm not sure if it was burning coolant but we decided to put a new headgasket in it. The old one did look like it had a break, so we decked the head and put it back together with new gaskets.

Well that didn't fix it, so we took it to the ford dealership in town. They did some diagnosing and told us it was a leaky valve seal(which on a side note here, that doesn't make sense does it? A seal would leak oil, unless they meant the valve seat was leaking.), so we put a new head on from rock auto. That hasn't fixed it either.

At this point we're out of ideas on what it could be. What do you guys think it could be?

Id be doing a compression test and a leak down test and doing from there.

I don't expect the compression test will give much info, but it's worth finding out if there's an obvious discrepancy on that cylinder.

With the leak down test, you'll be able to either find out if the cylinder is loosing pressure somewhere, or rule out a compression issue and then be able to focus on fuel and ignition issues.