I have witnessed this personally with a TA49 vs. stock turbo. At 18 psi, the TA49 ran identical ET and almost identical mph to a stock turbo at 18 psi. Up until that moment I had been convinced by others that a larger turbo allows you to run less boost and make more power. Turns out that is a myth, especially when you are comparing a larger turbo to a stock turbo in its "sweet spot" of 17-18 psi. Only when I started turning up the boost did the curves diverge. 22-23 psi is the "sweet spot" for a TE44.
Porting the heads or using a cam lowers the "crossover point" where a larger turbo makes measurably more power at a given boost level than a smaller turbo.