Originally Posted by Roelof

I wonder how well this works.....
There is already a 1mm space on that gap where the shim needs to be placed. The space is needed to give the manifold some flexibility, not only the movement but also to deal with a slight different mounting angle. Not knowing how thick the shims are but the first will for sure not give an extra length as the shim suggest because the 1mm gap.
The shim will also loosen the sealing on the large ring of the coupling rubber.