The ze22 engine uses a fly by wire throttle, have Vocky or someone port it for you. You will wonder why they were not done this way at the production stage.
Air filter £35/£40 panel
Cold air feed(s) to air box Top whack £20, mine was a £5.
Precat remove = free if done yourself.
200 cell sports cat from £75 to £150 plus fitting.
Port the throttle body, guessing £40 to £60, can do yourself with minimal tools.
Guess 11 to 13hp at this point being conservative.
2.4 Inlet manifold, stick your name on the list for a group buy, US say 13hp increase with induction kit and cat back exhaust.
These are good grounds and can be done a bit at a time. There are other mods inc cat back exhaust and inlet pipe from air box to throttle body and EGR pipe removal etc.
Only after you have settled for what you want from above i would entertain a remap or better still a live remap.
Where are you?