With a bigger throttle body one of two things is necessary. To obtain the best results you either need to port the intake manifold or utilize a tapered spacer. Shown above is a .243" polymer spacer, that is ported on one side to the throttle body and on the other side it is ported to the manifold. If you look closely, you can see the taper.
The key to an effective spacer is to have both sides perfectly flat. If the spacer is not flat, air can leak under boost costing you performance.
Once you have a piece to work with all that is left is to cut your tapered hole. Based on your two measurements calculate the angle that is needed. Cut the hole a few hundredths larger than you need. When the spacer is under compression it will shrink slightly and fit correctly. The amount of compression varies depending on your material and thickness.