Remember the Novarossi 5/6/7 fin manifolds? Those fins are just about 2.5~3mm separated and you could feel a huge difference between them. I made them from 1mm teflon and can stack up 2 of them behind the rubber seal. On the exhaust side the dimensions are different but if I make them for there too I could go up to 4mm extra length, that for sure will be a lot to notice.

But I believe the MR05 manifold that is in the combo package is a short one so I believe with these shims something will be noticeable. And as the tekst says, it is a finetune.