This is my DD and I really have no plans to upgrade the turbo (maybe upgraded stock turbo later), but..

I was thinking intake/exhaust manifold (probably megan)? Or should I go for springs/internals?

What kind of gains would I get from the intake/manifold?

Current mods:
Intake
FMIC, LICP/UICP
HKS Cams
255 fuel pump
o2 Housing/DP/Exaust
Stock springs/valves
Tuned