I ported and polished my lower intake of my GT40 upper and lower combination. It made such a difference! I took a gasket that matched my heads, stuck them down to the head. Put on my intake with some glue so the gaskets would stick to the intake. Pulled the intake off when the glue was dry. I then marked the intake where the gaskets were. Took off the gasket, then took a carbide bit and die grinder then WENT TO TOWN! :green Afterwards, I took a flap wheel with 60 grit sandpaper, cleaned it all up. It made such a difference it was incredible. I didn't think it would but it did.