O.E. material?? you mean the carpet joot? it's called joot (or however you want to spell it).
dynamat sucks. Back in the day when it was the only option it was the **** but in reality it is ****. If it doesn't heat right it wont adhere, if the surface isn't spotless it won't stay adhered.
If you get dynamat, get their spray can adhesive.
A better way (and cheaper!) to sound deaden is to:
1. Get paintable undercoating and spray it all over the bare body/inner doors after you pull out the interior panels
2. get a big can of 3M (not the cheap stuff, the $7 can) trim adhesive and some of the thickest "MIL" plastic sheeting from lowe's or home depot you can. Cut pieces in the shapes of the body panels/door panels, spray the adhesive on it let it tack then apply to the panels.
3. Re-joot over these plastic cutouts if yours was missing or nasty when you took the body panels off.
Enjoy the extra sound deadening and weight your car now has.