How long have you had the car?
Where does it stand with the timing chain ; does service book mention a change recently? (last few years)
If history shows no chain replacement, or there is no history - my only advice is to aim to get that done first, unfotunately lol.
If otherwise it has then goodo.
I think as with any n/a car with o.e management - best doing the tuning in stages.
Start with: *air filter- de-restrict and bigger feed or replace lot with dbilas flow master kit. *polish and ported throttle body. *de precat in the downpipe. *remove egr *cat back exhaust (2.25") *remap.
After that you could add: *chris tullet exhaust manifold, *2.25" downpipe with 200 cell CAT, then 2.25" throughout rest of system. *piper reground cams or courtney competition cams, *2.4 U.S inlet manifold. *remap.
Never going to be cheap or easy to turbo/ superchg any engine , reliably really.