On my e12 635, the fire wall insulation was not available. Made my own by first making a paper template and then cutting a bottom layer from 3/8" dense cell foam which I glued to the firewall with hi grade contact cement. I then cut the top layer from 3/16" neoprene and
laminated it to the dense cell foam. About $60 worth of material, and if I didn't let anyone know, I doubt they would know the difference. I did the interior of my firewall the same way, and also fixed the floor padding, by splicing into what remained, in decent condition, of the original padding