A big bore throttle body should not be used on a manifold that has not been bored to match or exceed the diameter of the throttle body (ie, a 70mm throttle body can be used on a manifold that’s bored to 74mm, but not on a manifold that’s bored to 65mm)

If you intend to bore the manifold yourself, use the supplied plastic gasket to trace out the bore before removing the studs.

Remove the gasket and check to see that the traced circle as shown in the figure.