Mobius is correct. Two strokes rely on sonic wave activity and those pressure waves travel at the speed of sound. Reed valves help by allowing the inlet to be open when it wants to be without the detrimental low speed impact of long duration ports. Exhaust valves are similar in that at lower engine speeds the valve is down (mild porting) and as revs rise, the valve lifts to more or less TZ race bike levels. That variability really helps to make more top end and not lose any mid range.
The other trick is to add capacity. A bigger motor at the same level of tune will make more power and torque than a small motor. With the 400, Yamaha went for a long stroke crank and that doesn't allow such high revs but on the street it loses nothing at the top and makes a lot more low down.
Getting more mid range is the sweet spot for the street and the usual solutions are an exhaust tuned for mid range - avoid race pipes, and more compression helps too, until it's too much. If you raise the exhaust ports you lose low speed compression so raising it helps on the street but at high revs it needs to be managed. That's where squish geometry can help too. Wide, thin squish bands raise MSV and that helps low to mid but at high revs it needs to be thicker and less wide to reduce MSV.
2 strokes can often use more ignition advance at low revs and low throttle settings so a fully programmable ignition is a useful tool.
Faster burning chemical soup type race gas can help too, but hard to get at a gas station off the Grossglockner pass I suspect.
Different reeds can also change the power band, but the effect is subtle. Try the YZ125 reed trick or even old school Boyesens to see what difference they make on your bike.
You could also try reed spacers https://www.economycycle.com/product-category/yamaha-rd250350400r5ds6ds7-parts/fuel-and-airintake/reeds-spacers/
The other trick is to add capacity. A bigger motor at the same level of tune will make more power and torque than a small motor. With the 400, Yamaha went for a long stroke crank and that doesn't allow such high revs but on the street it loses nothing at the top and makes a lot more low down.
Getting more mid range is the sweet spot for the street and the usual solutions are an exhaust tuned for mid range - avoid race pipes, and more compression helps too, until it's too much. If you raise the exhaust ports you lose low speed compression so raising it helps on the street but at high revs it needs to be managed. That's where squish geometry can help too. Wide, thin squish bands raise MSV and that helps low to mid but at high revs it needs to be thicker and less wide to reduce MSV.
2 strokes can often use more ignition advance at low revs and low throttle settings so a fully programmable ignition is a useful tool.
Faster burning chemical soup type race gas can help too, but hard to get at a gas station off the Grossglockner pass I suspect.
Different reeds can also change the power band, but the effect is subtle. Try the YZ125 reed trick or even old school Boyesens to see what difference they make on your bike.
You could also try reed spacers https://www.economycycle.com/product-category/yamaha-rd250350400r5ds6ds7-parts/fuel-and-airintake/reeds-spacers/