2 plug or not 2 plug

For those with rear ported speakers, do you use the foam plugs or not? Why, or why not? What have you learned as you have tested them in your system?
I would like to reactivate this thread as I would like to know this too, more specifically are most rear-ported speakers responding the same way to a foam plug? is foam density and plug length speaker specific or can one use any plug that fit in (say a ProAc plug into a Silverline monitor? is this a modification of the speaker freq resposne that can have negative effects elsewhere in the freq spectrum?
I have Totem Hawks with a small rear port and although I can achieve flatter bass response with a foam plug, it takes away some mid-range detail that I cannot live without - so no plugs for me. Have tried various densities of plugs too.

Just my experience in my room with my speakers.