Turboman
Mab An Gov
I've just done one on the trans tunnel (well, actually the whole of the front floor of the cab) - actually made quite a difference, but not enough - hadn't considered the bonnet - there's such a whopping big gap around it that it doesn't seem worth it?
Try it, makes a huge difference. And soundproofing is all about weight. The proper sound mat is very heavy. Cheap foam etc doesnt do the same.