3.8 L 100500 miles... Misfire cylinder #4 at idle

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REcently replaced OEM spark plugs, and wires, fuel injector for cylinder #4 along with o-rings for all injectors.. replaced upper intake manifold gaskets as well with injector repair. Cleared cat converter, no it is open, recovered plenty of power, and improved fuel trim.. still has a constant misfire at idle. Throttle response is good, full rpm range performance, dedicated misfire cylinder # 4. New engine air filter, cleaned throttle body, egr seems closed, pipe does not get hot... purge valve opens & closes.. did not run elec diag on wire harness.. injectors pulsing well.. Thinking of blocking egr, and pulling front valve cover to inspect springs, not sure where else to go.