I matched my LIM to my heads, which were gasket matched. My LIM has also been heavily ported/reshaped up to the holes the secondary shaft used to run through.

The top half of the LIM is split port (though it has been gasket matched...), but the center divider is knife edged/ported into an elliptical shape all the way up to the old hole for the secondary shaft, so that the final LIM port shape is just like the tumble port head.

I've got dyno proof that it hasn't hurt me at all, infact I've got a lot more torque than simular setups at the same psi.

2005 Ford F150 SuperCab FX4 1964 Chevrolet Impala SS 1998 CSVT: 354HP/328TQ @ 10 psi, now gone