2015 GL350 Bluetec, I'm trying to replace glow plug #6 (drivers side, rear-most plug) and there is just no room back in there. There are some firewall insulation / sound deadening panels in the way, but I'm not sure how to remove them. There is one on either side that are easily removed when replacing the air filters. But then there is one in the very center that I cannot see how to remove it. This center one is what's in the way.

Does anyone know how to remove the center firewall insulation / sound deadening panel on the firewall of x166 chassis?

Thank you in advance.