Did you use steps 1 thru 11 under "Simplified and Consolidated Pictorial for DBV #3" in the very middle of page 1 of the Incremental mods thread as your guide? I followed these steps and I didn't need to open mine again to tune them. They were vastly improved..
You should hear a significant improvement without any burn in.
First, if you're going to be working on these a bit, make your life a little easier by cutting out the four posts. A set of side cutters does a decent job and then its easier to do a nice neat job of putting the cotton and fiberglas in and you won't have to fool with cutting so many slots in the cotton/fiberglas.
You might need to cut the holes in the stiffened felt with a hole punch rather than just poking them in. I made 4 6mm holes with a hole punch. My holes ended up being mostly over the magazine paper treble reflector but I still get plenty of low bass. I also left the ear side bass vent open.
Try a magazine paper treble reflector? I used a 20 mm disk. It should improve the treble.
Other than what I have mentioned, I would suggest you try varying the thickness of the cotton/fiberglass.
Keep us apprised of your progress.
everything chinook9 says ... if you follow the recipe & use exactly the same materials identified in the recipe, then it's like shooting fish in a barrel ... bluemonkeyflyer's guide is literally foolproof. if things sound muffled, my first guess would be an overindulgence of stuffing (cotton/fiberglass).