Gasket Matching for Low Cost Horsepower Gains
Just use a new stock lower intake gasket and a Sharpie to mark off the areas of opportunity. Then use a combination of HAND files to get everything opened up nice and smooth. Even by hand the actual modifications only take an hour or so, so the extra time invested is worthwhile. With a power cutter of any type, it's just too easy to make a mistake when carving out soft aluminum.
NOTE: If your cylinder heads are still stock, this mod is NOT for you. If you make the intake ports larger than the cylinder head ports via gasket matching, you will actually LOSE power due to airflow disruption!