Another easy fix would be to use a plastic pipe in the desired outer diameter, scuff one end to fit the intake to some extend, heat the scuffed end to the melting point and push it back in for a closer fit, let it cool off, take it out and add a super thin layer of Vaseline to the pipe and inside of the intake, put it back in and it should stay centered, heat some expanded polystyrene foam (the white packaging stuff) to 240 degrees Celsius, poor it in, let it cool off, pull out, remove pipe, make flush, clean and install.

You can also use polyethylene w/ a melting point of 115 degrees C, or polypropylene at 160 degrees.

Try at your own risk