To my knolleg the m42 and m44 engine has forged internals. But they are not fully balanced. To balance what is done is they polish the surfaces carfully removing very small amounts to balance the parts. This should be done by a reputable proffesional. One misstake and you will need new parts or get a bad running engine.
port and polish means they make the ports bigger but don't make the valves bigger. They then polish the internals and reshape them to improve combustion.
These are actually best done to a 1.8L M42 engine because it increases the power with out going over 1.8L allowing you to compete in the 1.8L division in motorcross and autocross. Doing both brings the engine to about 190-200hp I will have my car dyno soon but can't get print out or else my friend can't do it for free.
Giving an engine a bore or a superchrager or turbo weakin the engine which should only be done if you intend on making a race only car.