Looks like a bit of a challenge. You could try doing what I've done and use a heat resistant foam that you can purchase from Clark Robber, or any other foam place. The one I'm using is 1.5cm thick, and can be bent and cut any way you like.
Just like SK said, first make up a cardboard template (doing it in three or four sections is easier then one large one), cut out the holes for the piping and the air flow meter and then just transfer it onto the foam. Then just take everything off and put it through the holes, and you should get a very good seal.
Although it may not be a substitute for a proper heat shield, this stuff works well and should cost you less then $30 plus an hour or so of your time.
Cheers
Daniel