do you have a 7,8 or 9 or infact as the pic suggests a 4, im a little confused from you other post now, as to what you have at the moment and what your looking to acheive, you said somthing about reaching 400 and you said about an engine swap but i think theres some confusion with the roman numerals
td05 is the type/style of flange that attaches to the manifold. I know a 20g is bigger than a 16g so gotta be to do with airflow.... The 10.5t hotside is also bigger than a 9.8t hotside. So again more air flow. The 4 has a small 9.0t hotside. It would also be better to have a single flapper not the twin so it can hold better boost
In either case, the IV turbo is the smallest so anything will be better but if you want a faster spool up then the HRA will be the best one to go for and they are relatively cheap.
You will not see more gains in power at all, you will just get there a little quicker.