Stephen, If you take the rear bumper off, have a look in behind it, what you will see is a faint line and indents, this is for the cut-out, all you need to do is drill out the holes and cut the along the dotted lines, easy.
Also, it you get a proper heat shield, it will come or should come with the insulator behind it, but I think these are very hard to get a hold of.
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