I quick thought on the FAA and performance modifications. Polishing a port is no different from removing carbon from a cylinder. Removing material to balance flow is a modification of a factory or PMA part and would be subject to their raised eyebrows. Matching up parts by weight is done at the factory and so is matching the flow of injectors (Continental has been doing that for the last few years now, so GAMI is becoming redundant). As long as you are using factory or PMA parts, the order you put them in is of no concern to the FAA. If you want to go through a pile of parts to match them in weight, it is fine. If you start modifying them in any way, you step over the line.
Flowing an engine is a nice touch, but if you do not flow the entire induction system, you may be wasting your time. Lots of mods are excellent at the start, but as you operate they loose their effectiveness. Intakes do get quite grimy, how often do you clean it out? K&N has jumped into the aircraft market. They have excellent flow numbers when they are new or clean. However they clog and loose flow logarithmically when they get dirty. Paper filters, while not as easy flowing when new, loose their flow in a linear fashion. K&N can be cleaned and re-coated, but you have to pay attention or it may be a flow reducer.
Balancing your prop and engine dynamically is one way to get a smooth engine. You do need to repeat it at least annually, props erode and engines wear. so keeping that up is important if you want smooth. Lots of folks run their props over the overhaul times. Not really a good idea. You want to check for corrosion, get new seals and ensure the profiles of the blades are matching. If they don't, they do not track in the same plane. This can cause roughness and lessened performance. Like tires, props are where the metal meets the air. Make it all it can be.