Have you checked the vacuum lines between your PCV, Canister and intake manifold? It sounds weird but that can cause idle walking.

How hard did you run it when it was turboed? It could be a rocker arm.

When you did the new N/A build do you take a look at all of your contact surfaces in your timing/valve assembly? That's one thing about the VTEC heads is they tend to develope idle issues when there's uneven wear between the rocker arm and the cam lobes (even just one).