Rough Idle 2005 mustang V6

There is an old thread here that deals with the same issue but it was rather old so I thought I would ask for myself. Here's what I've done

Cleaned the MAF

Cleaned the throttle body

While removing the throttle body I noticed that the gasket between the throttle body and the engine is missing, I'm far from a pro at this so i'm not sure how important that is. Any help would be great