Well it could be that the particular scenario that puts oil in the ports doesn't happen at/near idle. Could only happen when you slam the throttle closed after a WOT run when vacuum spikes. IDK if that is it at all, but my message is that in 30-40 seconds you may not have tested all common operating situations.

 

Sorry, didn't make myself clear. After 30-40 seconds at idle there was already oil in most ports, but it wasn't clear where it's coming from. No clear traces of oil from rocker holes unfortunately

 

Just to update with solution to the problem...
Reason was bad valley cover gasket

 

Really? I am having a hard time picturing how that equates to oil in the intake ports. Draw my feeble mind a mental picture? Glad you fixed the problem either way.

 

Leaky valley cover and leaky intake manifold...?

 

I had that thought but figured ALL the intake o-rings weren't leaking.

 

Sorry for confusion guys. All on the OUTSIDE of the engine (which I thought was coming from HG's) was leaking from valley cover.