I haven't seen anything really posted on this yet.  so here it is.

I have played several games now against the AI with friends and after taking removing all Alien influence from a world by destroying his structures and the planet pop. the Culture is not detracting from the world. its staying constant.  This even happens when you have a fleet of Cap-ships in the gravity well which is supposed to remove the Alien influance, this also causes you to not be able to take over the world. 

I have also noticed this on my planets when I have a culture building built in the grav-well and the alien culture is piercing through my world to another.  Even after building the media center the influence will not detract.  I have however noticed that once I build more then one media center in the well it does after a period of time start removing their influance.

I still have Save games if needed.

OK, nice. I did look into the Known issues of Yarlens and did not set this listed there.  Maybe it should be.

Thanks guys,

Iva seen some games wher culture lingered... but it was because I had invested in the culture lingering upgrades. eventually it did go away.