The mitsi TD04HL is a small turbo, same as what is on the 1800 Lancer GSR's.
There aren't any upgrades that can be done to them that are worth it to these turbos.
If you used a TD05H from a VR-4 or EVO that would be a better starting point and they can be modded with TD06 & Garrett parts to support upto 500hp.