Well, for starters you can swap out the air intake with long ram performance ones (also a bigger exhaust), that will "inflate" the torque curve a bit throughout the rpm band but dont expect any more than 1-2 peak HP increase. Moving on, keeping the engine naturally aspirated, you can modify ECU map to adjust the AFR (air fuel ratio) but that will only inflate the lower portion of the torque curve. You can also modify ECU map to adjust other parameters such as intake/exhaust valves timings to get some performance gains. Now if you want some serious gains then you have to go down the forced induction path either by a turbo or a super charge, but that will be quite expensive.
About ECU remaps, I know that some enthusiast garages do that for honda but I have no idea for toyota but it is possible. You can also gain some performance gains by using thinner engine oil such as 0w20 if it is recommended by the manufacturer for the engine in your car
And btw 0-100 timing doesnt tell the whole story and you cannot assume the same acceleration for 100-200 kmph, now I dont want to start yaris vs civic war but you might get my point. If 0-100 was a concern then pdkm wagonr 1.0 litre does it in 10-11 seconds
