I don't actually understand the prices for these products, it's a piece of high density foam with some foil backing and if you're lucky some adhesive backing.
I am going to be stripping the 90 down in a few weeks for a full inside & out respray, I indend on doing some SERIOUS soundproofing to it when it's in pieces and I will be looking into all sorts of products to achieve this, however, when it comes to the engine bay I will need to bite the bullet and buy the good stuff as I don't want melted goo dripping from my bonnet and bulkhead!
I am going to put 12mm insulation on the bulkhead enginebay side, and put 25mm stuff in the passenger footwells and probably just 12mm in the driver side (25mm will probably cause pedal issues, I am going to do the transmission tunnel inside and out and I am going to get the floor panels coated in that heavy rubber stuff on the underside, the seatbox too.
I'll probably end up spending more on soundproofing than anything else!
Oh - does anyone have any 90 tub cappings in good nick? Don't care about the paint as they will be going for galv.