TiAg

Update. It was the injector! Ended up replacing all 6 though. no problems since.

Just to add we narrowed it down to no.6 cylinder. Spark is good when it decides to play up. and compression is a perfect 180psi. So it's gotta be fuel injector or related to what drives it, ECM?. Or something else is telling cylinder 6 not to inject fuel. Crankshaft sensor?

Sorry for bumping an old thread. I have exact same issue as described done some of the same work plugs,Leads,Coils, Fuel filter. Almost seems like it shuts an injector off. For a test when its running good i pulled one injector plug while it was running and i acted sounds the exact same as when i plays up.