Porting and Polishing..
 

a 1.0L intake? Any expected gains?

I would think that there would be some gains if done properly. For the sake of FE, don't go too crazy on porting the intake side. If you do, the velocity will be reduced and there won't be as much swirl and combustion efficiency may suffer.

Better left alone then, hmm?

I might work on porting the exhaust side a bit but would be careful to not do much more than smooth out the edges on the intake. Port matching between the manifolds and the head is good too. Since you've got it apart you may want to look into Power Lynz in the intake ports. They are basically screw threads that introduce swirl into the intake stream. Check this out for more info. https://powrehaus.com/cylinder-head-porting/ He's a good friend of mine and did a bunch of free work on my '99 Saturn SL2.

I meant the intake manifold, not the intake channel on the head..

The way I did mine was smooth out the radius on the bottom of the ports. Clean up around the valve and port match the head to the intake and exhaust. You really don't want to remove much more metal than you have to opening up the runners keeping them small is better. The exhaust on mine had a lot of casting junk that needed cleaned. Also polish the exhaust side as much as you can to keep the carbon buildup off it. Polishing the combustion chamber is also a good thing and can let you get away with some more ignition timing possibly.

Take the intake manifold and clean and smooth it out as well. The throttle body has a little bit that can be done to improve it. The exhaust manifold is actually pretty decent but you can smooth the casting marks and stuff on it as well.