I've removed some of the liner towards the back, It was sagging down and melting to my transmission. I can hear more engine noise but that could also be the single mass flywheel conversion. I'm very tempted to remove it all, it's in very bad condition but I'm worried about cabin heat as I don't have A/C.
I believe you can still buy this liner at a moderate price. You could always remove it and if you're unhappy order a new liner. If you go that route let us know how it works out.