You have to look at it differently.
At the old peak of 2800 rpm, torque has increased from 200 ft. lbs to 226 ft. lbs. There is still an increase (pretty good one), it's just that the PEAK is higher (2800 to 4300 rpm). It's the same way with the horsepower. At the old peak (4800 rpm), it has gone from 170 hp to 215 hp with the mods. This is a healthy increase. The better increase in power at higher rpm is just natural - you get more gas and air going through an engine and you are going to get more power.
I guess another option would be supercharging?

------------------