Mike is right. I did the same thing on an arm. I pressed the rubber out of the metal sleeve and fluid spilled everywhere. OEM is still fluid filled as far as I can tell.
So far everyone has been loving the OEM arms with the HD bushings. I wouldn't be scared to run the TRWs. Max is right, TRW is OEM on a lot of BMW parts. I sell a ton of them and have had zero complaints. I only have the Lems on the site because there are a few that still want them.
Pressing the bushings is a PITA and time consuming. You also run the risk of destroying your bushing and/or arms. If I could buy arms without the OEM bushings then I'm sure they'd be cheaper. What you are basically paying for is 2 sets of bushings. The OEMs I have to press out and then the HDs I press in.